2018-03-01 Paul Thomas <pault@gcc.gnu.org>

[official-gcc.git] / libgo / go / testing / testing.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package testing provides support for automated testing of Go packages.
// It is intended to be used in concert with the ``go test'' command, which automates
// execution of any function of the form
//     func TestXxx(*testing.T)
// where Xxx does not start with a lowercase letter. The function name
// serves to identify the test routine.
//
// Within these functions, use the Error, Fail or related methods to signal failure.
//
// To write a new test suite, create a file whose name ends _test.go that
// contains the TestXxx functions as described here. Put the file in the same
// package as the one being tested. The file will be excluded from regular
// package builds but will be included when the ``go test'' command is run.
// For more detail, run ``go help test'' and ``go help testflag''.
//
// Tests and benchmarks may be skipped if not applicable with a call to
// the Skip method of *T and *B:
//     func TestTimeConsuming(t *testing.T) {
//         if testing.Short() {
//             t.Skip("skipping test in short mode.")
//         }
//         ...
//     }
//
// Benchmarks
//
// Functions of the form
//     func BenchmarkXxx(*testing.B)
// are considered benchmarks, and are executed by the "go test" command when
// its -bench flag is provided. Benchmarks are run sequentially.
//
// For a description of the testing flags, see
// https://golang.org/cmd/go/#hdr-Description_of_testing_flags.
//
// A sample benchmark function looks like this:
//     func BenchmarkHello(b *testing.B) {
//         for i := 0; i < b.N; i++ {
//             fmt.Sprintf("hello")
//         }
//     }
//
// The benchmark function must run the target code b.N times.
// During benchmark execution, b.N is adjusted until the benchmark function lasts
// long enough to be timed reliably. The output
//     BenchmarkHello    10000000    282 ns/op
// means that the loop ran 10000000 times at a speed of 282 ns per loop.
//
// If a benchmark needs some expensive setup before running, the timer
// may be reset:
//
//     func BenchmarkBigLen(b *testing.B) {
//         big := NewBig()
//         b.ResetTimer()
//         for i := 0; i < b.N; i++ {
//             big.Len()
//         }
//     }
//
// If a benchmark needs to test performance in a parallel setting, it may use
// the RunParallel helper function; such benchmarks are intended to be used with
// the go test -cpu flag:
//
//     func BenchmarkTemplateParallel(b *testing.B) {
//         templ := template.Must(template.New("test").Parse("Hello, {{.}}!"))
//         b.RunParallel(func(pb *testing.PB) {
//             var buf bytes.Buffer
//             for pb.Next() {
//                 buf.Reset()
//                 templ.Execute(&buf, "World")
//             }
//         })
//     }
//
// Examples
//
// The package also runs and verifies example code. Example functions may
// include a concluding line comment that begins with "Output:" and is compared with
// the standard output of the function when the tests are run. (The comparison
// ignores leading and trailing space.) These are examples of an example:
//
//     func ExampleHello() {
//         fmt.Println("hello")
//         // Output: hello
//     }
//
//     func ExampleSalutations() {
//         fmt.Println("hello, and")
//         fmt.Println("goodbye")
//         // Output:
//         // hello, and
//         // goodbye
//     }
//
// The comment prefix "Unordered output:" is like "Output:", but matches any
// line order:
//
//     func ExamplePerm() {
//         for _, value := range Perm(4) {
//             fmt.Println(value)
//         }
//         // Unordered output: 4
//         // 2
//         // 1
//         // 3
//         // 0
//     }
//
// Example functions without output comments are compiled but not executed.
//
// The naming convention to declare examples for the package, a function F, a type T and
// method M on type T are:
//
//     func Example() { ... }
//     func ExampleF() { ... }
//     func ExampleT() { ... }
//     func ExampleT_M() { ... }
//
// Multiple example functions for a package/type/function/method may be provided by
// appending a distinct suffix to the name. The suffix must start with a
// lower-case letter.
//
//     func Example_suffix() { ... }
//     func ExampleF_suffix() { ... }
//     func ExampleT_suffix() { ... }
//     func ExampleT_M_suffix() { ... }
//
// The entire test file is presented as the example when it contains a single
// example function, at least one other function, type, variable, or constant
// declaration, and no test or benchmark functions.
//
// Subtests and Sub-benchmarks
//
// The Run methods of T and B allow defining subtests and sub-benchmarks,
// without having to define separate functions for each. This enables uses
// like table-driven benchmarks and creating hierarchical tests.
// It also provides a way to share common setup and tear-down code:
//
//     func TestFoo(t *testing.T) {
//         // <setup code>
//         t.Run("A=1", func(t *testing.T) { ... })
//         t.Run("A=2", func(t *testing.T) { ... })
//         t.Run("B=1", func(t *testing.T) { ... })
//         // <tear-down code>
//     }
//
// Each subtest and sub-benchmark has a unique name: the combination of the name
// of the top-level test and the sequence of names passed to Run, separated by
// slashes, with an optional trailing sequence number for disambiguation.
//
// The argument to the -run and -bench command-line flags is an unanchored regular
// expression that matches the test's name. For tests with multiple slash-separated
// elements, such as subtests, the argument is itself slash-separated, with
// expressions matching each name element in turn. Because it is unanchored, an
// empty expression matches any string.
// For example, using "matching" to mean "whose name contains":
//
//     go test -run ''      # Run all tests.
//     go test -run Foo     # Run top-level tests matching "Foo", such as "TestFooBar".
//     go test -run Foo/A=  # For top-level tests matching "Foo", run subtests matching "A=".
//     go test -run /A=1    # For all top-level tests, run subtests matching "A=1".
//
// Subtests can also be used to control parallelism. A parent test will only
// complete once all of its subtests complete. In this example, all tests are
// run in parallel with each other, and only with each other, regardless of
// other top-level tests that may be defined:
//
//     func TestGroupedParallel(t *testing.T) {
//         for _, tc := range tests {
//             tc := tc // capture range variable
//             t.Run(tc.Name, func(t *testing.T) {
//                 t.Parallel()
//                 ...
//             })
//         }
//     }
//
// Run does not return until parallel subtests have completed, providing a way
// to clean up after a group of parallel tests:
//
//     func TestTeardownParallel(t *testing.T) {
//         // This Run will not return until the parallel tests finish.
//         t.Run("group", func(t *testing.T) {
//             t.Run("Test1", parallelTest1)
//             t.Run("Test2", parallelTest2)
//             t.Run("Test3", parallelTest3)
//         })
//         // <tear-down code>
//     }
//
// Main
//
// It is sometimes necessary for a test program to do extra setup or teardown
// before or after testing. It is also sometimes necessary for a test to control
// which code runs on the main thread. To support these and other cases,
// if a test file contains a function:
//
//      func TestMain(m *testing.M)
//
// then the generated test will call TestMain(m) instead of running the tests
// directly. TestMain runs in the main goroutine and can do whatever setup
// and teardown is necessary around a call to m.Run. It should then call
// os.Exit with the result of m.Run. When TestMain is called, flag.Parse has
// not been run. If TestMain depends on command-line flags, including those
// of the testing package, it should call flag.Parse explicitly.
//
// A simple implementation of TestMain is:
//
//      func TestMain(m *testing.M) {
//              // call flag.Parse() here if TestMain uses flags
//              os.Exit(m.Run())
//      }
//
package testing

import (
        "bytes"
        "errors"
        "flag"
        "fmt"
        "internal/race"
        "io"
        "os"
        "runtime"
        "runtime/debug"
        "runtime/trace"
        "strconv"
        "strings"
        "sync"
        "sync/atomic"
        "time"
)

var (
        // The short flag requests that tests run more quickly, but its functionality
        // is provided by test writers themselves. The testing package is just its
        // home. The all.bash installation script sets it to make installation more
        // efficient, but by default the flag is off so a plain "go test" will do a
        // full test of the package.
        short = flag.Bool("test.short", false, "run smaller test suite to save time")

        // The failfast flag requests that test execution stop after the first test failure.
        failFast = flag.Bool("test.failfast", false, "do not start new tests after the first test failure")

        // The directory in which to create profile files and the like. When run from
        // "go test", the binary always runs in the source directory for the package;
        // this flag lets "go test" tell the binary to write the files in the directory where
        // the "go test" command is run.
        outputDir = flag.String("test.outputdir", "", "write profiles to `dir`")

        // Report as tests are run; default is silent for success.
        chatty               = flag.Bool("test.v", false, "verbose: print additional output")
        count                = flag.Uint("test.count", 1, "run tests and benchmarks `n` times")
        coverProfile         = flag.String("test.coverprofile", "", "write a coverage profile to `file`")
        matchList            = flag.String("test.list", "", "list tests, examples, and benchmarks matching `regexp` then exit")
        match                = flag.String("test.run", "", "run only tests and examples matching `regexp`")
        memProfile           = flag.String("test.memprofile", "", "write a memory profile to `file`")
        memProfileRate       = flag.Int("test.memprofilerate", 0, "set memory profiling `rate` (see runtime.MemProfileRate)")
        cpuProfile           = flag.String("test.cpuprofile", "", "write a cpu profile to `file`")
        blockProfile         = flag.String("test.blockprofile", "", "write a goroutine blocking profile to `file`")
        blockProfileRate     = flag.Int("test.blockprofilerate", 1, "set blocking profile `rate` (see runtime.SetBlockProfileRate)")
        mutexProfile         = flag.String("test.mutexprofile", "", "write a mutex contention profile to the named file after execution")
        mutexProfileFraction = flag.Int("test.mutexprofilefraction", 1, "if >= 0, calls runtime.SetMutexProfileFraction()")
        traceFile            = flag.String("test.trace", "", "write an execution trace to `file`")
        timeout              = flag.Duration("test.timeout", 0, "panic test binary after duration `d` (default 0, timeout disabled)")
        cpuListStr           = flag.String("test.cpu", "", "comma-separated `list` of cpu counts to run each test with")
        parallel             = flag.Int("test.parallel", runtime.GOMAXPROCS(0), "run at most `n` tests in parallel")
        testlog              = flag.String("test.testlogfile", "", "write test action log to `file` (for use only by cmd/go)")

        haveExamples bool // are there examples?

        cpuList     []int
        testlogFile *os.File

        numFailed uint32 // number of test failures
)

// common holds the elements common between T and B and
// captures common methods such as Errorf.
type common struct {
        mu      sync.RWMutex        // guards this group of fields
        output  []byte              // Output generated by test or benchmark.
        w       io.Writer           // For flushToParent.
        ran     bool                // Test or benchmark (or one of its subtests) was executed.
        failed  bool                // Test or benchmark has failed.
        skipped bool                // Test of benchmark has been skipped.
        done    bool                // Test is finished and all subtests have completed.
        helpers map[string]struct{} // functions to be skipped when writing file/line info

        chatty     bool   // A copy of the chatty flag.
        finished   bool   // Test function has completed.
        hasSub     int32  // written atomically
        raceErrors int    // number of races detected during test
        runner     string // function name of tRunner running the test

        parent   *common
        level    int       // Nesting depth of test or benchmark.
        name     string    // Name of test or benchmark.
        start    time.Time // Time test or benchmark started
        duration time.Duration
        barrier  chan bool // To signal parallel subtests they may start.
        signal   chan bool // To signal a test is done.
        sub      []*T      // Queue of subtests to be run in parallel.
}

// Short reports whether the -test.short flag is set.
func Short() bool {
        return *short
}

// CoverMode reports what the test coverage mode is set to. The
// values are "set", "count", or "atomic". The return value will be
// empty if test coverage is not enabled.
func CoverMode() string {
        return cover.Mode
}

// Verbose reports whether the -test.v flag is set.
func Verbose() bool {
        return *chatty
}

// frameSkip searches, starting after skip frames, for the first caller frame
// in a function not marked as a helper and returns the frames to skip
// to reach that site. The search stops if it finds a tRunner function that
// was the entry point into the test.
// This function must be called with c.mu held.
func (c *common) frameSkip(skip int) int {
        if c.helpers == nil {
                return skip
        }
        var pc [50]uintptr
        // Skip two extra frames to account for this function
        // and runtime.Callers itself.
        n := runtime.Callers(skip+2, pc[:])
        if n == 0 {
                panic("testing: zero callers found")
        }
        frames := runtime.CallersFrames(pc[:n])
        var frame runtime.Frame
        more := true
        for i := 0; more; i++ {
                frame, more = frames.Next()
                if frame.Function == c.runner {
                        // We've gone up all the way to the tRunner calling
                        // the test function (so the user must have
                        // called tb.Helper from inside that test function).
                        // Only skip up to the test function itself.
                        return skip + i - 1
                }
                if _, ok := c.helpers[frame.Function]; !ok {
                        // Found a frame that wasn't inside a helper function.
                        return skip + i
                }
        }
        return skip
}

// decorate prefixes the string with the file and line of the call site
// and inserts the final newline if needed and indentation tabs for formatting.
// This function must be called with c.mu held.
func (c *common) decorate(s string) string {
        skip := c.frameSkip(3) // decorate + log + public function.
        _, file, line, ok := runtime.Caller(skip)
        if ok {
                // Truncate file name at last file name separator.
                if index := strings.LastIndex(file, "/"); index >= 0 {
                        file = file[index+1:]
                } else if index = strings.LastIndex(file, "\\"); index >= 0 {
                        file = file[index+1:]
                }
        } else {
                file = "???"
                line = 1
        }
        buf := new(bytes.Buffer)
        // Every line is indented at least one tab.
        buf.WriteByte('\t')
        fmt.Fprintf(buf, "%s:%d: ", file, line)
        lines := strings.Split(s, "\n")
        if l := len(lines); l > 1 && lines[l-1] == "" {
                lines = lines[:l-1]
        }
        for i, line := range lines {
                if i > 0 {
                        // Second and subsequent lines are indented an extra tab.
                        buf.WriteString("\n\t\t")
                }
                buf.WriteString(line)
        }
        buf.WriteByte('\n')
        return buf.String()
}

// flushToParent writes c.output to the parent after first writing the header
// with the given format and arguments.
func (c *common) flushToParent(format string, args ...interface{}) {
        p := c.parent
        p.mu.Lock()
        defer p.mu.Unlock()

        fmt.Fprintf(p.w, format, args...)

        c.mu.Lock()
        defer c.mu.Unlock()
        io.Copy(p.w, bytes.NewReader(c.output))
        c.output = c.output[:0]
}

type indenter struct {
        c *common
}

func (w indenter) Write(b []byte) (n int, err error) {
        n = len(b)
        for len(b) > 0 {
                end := bytes.IndexByte(b, '\n')
                if end == -1 {
                        end = len(b)
                } else {
                        end++
                }
                // An indent of 4 spaces will neatly align the dashes with the status
                // indicator of the parent.
                const indent = "    "
                w.c.output = append(w.c.output, indent...)
                w.c.output = append(w.c.output, b[:end]...)
                b = b[end:]
        }
        return
}

// fmtDuration returns a string representing d in the form "87.00s".
func fmtDuration(d time.Duration) string {
        return fmt.Sprintf("%.2fs", d.Seconds())
}

// TB is the interface common to T and B.
type TB interface {
        Error(args ...interface{})
        Errorf(format string, args ...interface{})
        Fail()
        FailNow()
        Failed() bool
        Fatal(args ...interface{})
        Fatalf(format string, args ...interface{})
        Log(args ...interface{})
        Logf(format string, args ...interface{})
        Name() string
        Skip(args ...interface{})
        SkipNow()
        Skipf(format string, args ...interface{})
        Skipped() bool
        Helper()

        // A private method to prevent users implementing the
        // interface and so future additions to it will not
        // violate Go 1 compatibility.
        private()
}

var _ TB = (*T)(nil)
var _ TB = (*B)(nil)

// T is a type passed to Test functions to manage test state and support formatted test logs.
// Logs are accumulated during execution and dumped to standard output when done.
//
// A test ends when its Test function returns or calls any of the methods
// FailNow, Fatal, Fatalf, SkipNow, Skip, or Skipf. Those methods, as well as
// the Parallel method, must be called only from the goroutine running the
// Test function.
//
// The other reporting methods, such as the variations of Log and Error,
// may be called simultaneously from multiple goroutines.
type T struct {
        common
        isParallel bool
        context    *testContext // For running tests and subtests.
}

func (c *common) private() {}

// Name returns the name of the running test or benchmark.
func (c *common) Name() string {
        return c.name
}

func (c *common) setRan() {
        if c.parent != nil {
                c.parent.setRan()
        }
        c.mu.Lock()
        defer c.mu.Unlock()
        c.ran = true
}

// Fail marks the function as having failed but continues execution.
func (c *common) Fail() {
        if c.parent != nil {
                c.parent.Fail()
        }
        c.mu.Lock()
        defer c.mu.Unlock()
        // c.done needs to be locked to synchronize checks to c.done in parent tests.
        if c.done {
                panic("Fail in goroutine after " + c.name + " has completed")
        }
        c.failed = true
}

// Failed reports whether the function has failed.
func (c *common) Failed() bool {
        c.mu.RLock()
        failed := c.failed
        c.mu.RUnlock()
        return failed || c.raceErrors+race.Errors() > 0
}

// FailNow marks the function as having failed and stops its execution
// by calling runtime.Goexit (which then runs all deferred calls in the
// current goroutine).
// Execution will continue at the next test or benchmark.
// FailNow must be called from the goroutine running the
// test or benchmark function, not from other goroutines
// created during the test. Calling FailNow does not stop
// those other goroutines.
func (c *common) FailNow() {
        c.Fail()

        // Calling runtime.Goexit will exit the goroutine, which
        // will run the deferred functions in this goroutine,
        // which will eventually run the deferred lines in tRunner,
        // which will signal to the test loop that this test is done.
        //
        // A previous version of this code said:
        //
        //      c.duration = ...
        //      c.signal <- c.self
        //      runtime.Goexit()
        //
        // This previous version duplicated code (those lines are in
        // tRunner no matter what), but worse the goroutine teardown
        // implicit in runtime.Goexit was not guaranteed to complete
        // before the test exited. If a test deferred an important cleanup
        // function (like removing temporary files), there was no guarantee
        // it would run on a test failure. Because we send on c.signal during
        // a top-of-stack deferred function now, we know that the send
        // only happens after any other stacked defers have completed.
        c.finished = true
        runtime.Goexit()
}

// log generates the output. It's always at the same stack depth.
func (c *common) log(s string) {
        c.mu.Lock()
        defer c.mu.Unlock()
        c.output = append(c.output, c.decorate(s)...)
}

// Log formats its arguments using default formatting, analogous to Println,
// and records the text in the error log. For tests, the text will be printed only if
// the test fails or the -test.v flag is set. For benchmarks, the text is always
// printed to avoid having performance depend on the value of the -test.v flag.
func (c *common) Log(args ...interface{}) { c.log(fmt.Sprintln(args...)) }

// Logf formats its arguments according to the format, analogous to Printf, and
// records the text in the error log. A final newline is added if not provided. For
// tests, the text will be printed only if the test fails or the -test.v flag is
// set. For benchmarks, the text is always printed to avoid having performance
// depend on the value of the -test.v flag.
func (c *common) Logf(format string, args ...interface{}) { c.log(fmt.Sprintf(format, args...)) }

// Error is equivalent to Log followed by Fail.
func (c *common) Error(args ...interface{}) {
        c.log(fmt.Sprintln(args...))
        c.Fail()
}

// Errorf is equivalent to Logf followed by Fail.
func (c *common) Errorf(format string, args ...interface{}) {
        c.log(fmt.Sprintf(format, args...))
        c.Fail()
}

// Fatal is equivalent to Log followed by FailNow.
func (c *common) Fatal(args ...interface{}) {
        c.log(fmt.Sprintln(args...))
        c.FailNow()
}

// Fatalf is equivalent to Logf followed by FailNow.
func (c *common) Fatalf(format string, args ...interface{}) {
        c.log(fmt.Sprintf(format, args...))
        c.FailNow()
}

// Skip is equivalent to Log followed by SkipNow.
func (c *common) Skip(args ...interface{}) {
        c.log(fmt.Sprintln(args...))
        c.SkipNow()
}

// Skipf is equivalent to Logf followed by SkipNow.
func (c *common) Skipf(format string, args ...interface{}) {
        c.log(fmt.Sprintf(format, args...))
        c.SkipNow()
}

// SkipNow marks the test as having been skipped and stops its execution
// by calling runtime.Goexit.
// If a test fails (see Error, Errorf, Fail) and is then skipped,
// it is still considered to have failed.
// Execution will continue at the next test or benchmark. See also FailNow.
// SkipNow must be called from the goroutine running the test, not from
// other goroutines created during the test. Calling SkipNow does not stop
// those other goroutines.
func (c *common) SkipNow() {
        c.skip()
        c.finished = true
        runtime.Goexit()
}

func (c *common) skip() {
        c.mu.Lock()
        defer c.mu.Unlock()
        c.skipped = true
}

// Skipped reports whether the test was skipped.
func (c *common) Skipped() bool {
        c.mu.RLock()
        defer c.mu.RUnlock()
        return c.skipped
}

// Helper marks the calling function as a test helper function.
// When printing file and line information, that function will be skipped.
// Helper may be called simultaneously from multiple goroutines.
// Helper has no effect if it is called directly from a TestXxx/BenchmarkXxx
// function or a subtest/sub-benchmark function.
func (c *common) Helper() {
        c.mu.Lock()
        defer c.mu.Unlock()
        if c.helpers == nil {
                c.helpers = make(map[string]struct{})
        }
        c.helpers[callerName(1)] = struct{}{}
}

// callerName gives the function name (qualified with a package path)
// for the caller after skip frames (where 0 means the current function).
func callerName(skip int) string {
        // Make room for the skip PC.
        var pc [2]uintptr
        n := runtime.Callers(skip+2, pc[:]) // skip + runtime.Callers + callerName
        if n == 0 {
                panic("testing: zero callers found")
        }
        frames := runtime.CallersFrames(pc[:n])
        frame, _ := frames.Next()
        return frame.Function
}

// Parallel signals that this test is to be run in parallel with (and only with)
// other parallel tests. When a test is run multiple times due to use of
// -test.count or -test.cpu, multiple instances of a single test never run in
// parallel with each other.
func (t *T) Parallel() {
        if t.isParallel {
                panic("testing: t.Parallel called multiple times")
        }
        t.isParallel = true

        // We don't want to include the time we spend waiting for serial tests
        // in the test duration. Record the elapsed time thus far and reset the
        // timer afterwards.
        t.duration += time.Since(t.start)

        // Add to the list of tests to be released by the parent.
        t.parent.sub = append(t.parent.sub, t)
        t.raceErrors += race.Errors()

        if t.chatty {
                // Print directly to root's io.Writer so there is no delay.
                root := t.parent
                for ; root.parent != nil; root = root.parent {
                }
                root.mu.Lock()
                fmt.Fprintf(root.w, "=== PAUSE %s\n", t.name)
                root.mu.Unlock()
        }

        t.signal <- true   // Release calling test.
        <-t.parent.barrier // Wait for the parent test to complete.
        t.context.waitParallel()

        if t.chatty {
                // Print directly to root's io.Writer so there is no delay.
                root := t.parent
                for ; root.parent != nil; root = root.parent {
                }
                root.mu.Lock()
                fmt.Fprintf(root.w, "=== CONT  %s\n", t.name)
                root.mu.Unlock()
        }

        t.start = time.Now()
        t.raceErrors += -race.Errors()
}

// An internal type but exported because it is cross-package; part of the implementation
// of the "go test" command.
type InternalTest struct {
        Name string
        F    func(*T)
}

func tRunner(t *T, fn func(t *T)) {
        t.runner = callerName(0)

        // When this goroutine is done, either because fn(t)
        // returned normally or because a test failure triggered
        // a call to runtime.Goexit, record the duration and send
        // a signal saying that the test is done.
        defer func() {
                if t.raceErrors+race.Errors() > 0 {
                        t.Errorf("race detected during execution of test")
                }

                t.duration += time.Since(t.start)
                // If the test panicked, print any test output before dying.
                err := recover()
                if !t.finished && err == nil {
                        err = fmt.Errorf("test executed panic(nil) or runtime.Goexit")
                }
                if err != nil {
                        t.Fail()
                        t.report()
                        panic(err)
                }

                if len(t.sub) > 0 {
                        // Run parallel subtests.
                        // Decrease the running count for this test.
                        t.context.release()
                        // Release the parallel subtests.
                        close(t.barrier)
                        // Wait for subtests to complete.
                        for _, sub := range t.sub {
                                <-sub.signal
                        }
                        if !t.isParallel {
                                // Reacquire the count for sequential tests. See comment in Run.
                                t.context.waitParallel()
                        }
                } else if t.isParallel {
                        // Only release the count for this test if it was run as a parallel
                        // test. See comment in Run method.
                        t.context.release()
                }
                t.report() // Report after all subtests have finished.

                // Do not lock t.done to allow race detector to detect race in case
                // the user does not appropriately synchronizes a goroutine.
                t.done = true
                if t.parent != nil && atomic.LoadInt32(&t.hasSub) == 0 {
                        t.setRan()
                }
                t.signal <- true
        }()

        t.start = time.Now()
        t.raceErrors = -race.Errors()
        fn(t)

        if t.failed {
                atomic.AddUint32(&numFailed, 1)
        }
        t.finished = true
}

// Run runs f as a subtest of t called name. It runs f in a separate goroutine
// and blocks until f returns or calls t.Parallel to become a parallel test.
// Run reports whether f succeeded (or at least did not fail before calling t.Parallel).
//
// Run may be called simultaneously from multiple goroutines, but all such calls
// must return before the outer test function for t returns.
func (t *T) Run(name string, f func(t *T)) bool {
        atomic.StoreInt32(&t.hasSub, 1)
        testName, ok, _ := t.context.match.fullName(&t.common, name)
        if !ok || shouldFailFast() {
                return true
        }
        t = &T{
                common: common{
                        barrier: make(chan bool),
                        signal:  make(chan bool),
                        name:    testName,
                        parent:  &t.common,
                        level:   t.level + 1,
                        chatty:  t.chatty,
                },
                context: t.context,
        }
        t.w = indenter{&t.common}

        if t.chatty {
                // Print directly to root's io.Writer so there is no delay.
                root := t.parent
                for ; root.parent != nil; root = root.parent {
                }
                root.mu.Lock()
                fmt.Fprintf(root.w, "=== RUN   %s\n", t.name)
                root.mu.Unlock()
        }
        // Instead of reducing the running count of this test before calling the
        // tRunner and increasing it afterwards, we rely on tRunner keeping the
        // count correct. This ensures that a sequence of sequential tests runs
        // without being preempted, even when their parent is a parallel test. This
        // may especially reduce surprises if *parallel == 1.
        go tRunner(t, f)
        <-t.signal
        return !t.failed
}

// testContext holds all fields that are common to all tests. This includes
// synchronization primitives to run at most *parallel tests.
type testContext struct {
        match *matcher

        mu sync.Mutex

        // Channel used to signal tests that are ready to be run in parallel.
        startParallel chan bool

        // running is the number of tests currently running in parallel.
        // This does not include tests that are waiting for subtests to complete.
        running int

        // numWaiting is the number tests waiting to be run in parallel.
        numWaiting int

        // maxParallel is a copy of the parallel flag.
        maxParallel int
}

func newTestContext(maxParallel int, m *matcher) *testContext {
        return &testContext{
                match:         m,
                startParallel: make(chan bool),
                maxParallel:   maxParallel,
                running:       1, // Set the count to 1 for the main (sequential) test.
        }
}

func (c *testContext) waitParallel() {
        c.mu.Lock()
        if c.running < c.maxParallel {
                c.running++
                c.mu.Unlock()
                return
        }
        c.numWaiting++
        c.mu.Unlock()
        <-c.startParallel
}

func (c *testContext) release() {
        c.mu.Lock()
        if c.numWaiting == 0 {
                c.running--
                c.mu.Unlock()
                return
        }
        c.numWaiting--
        c.mu.Unlock()
        c.startParallel <- true // Pick a waiting test to be run.
}

// No one should be using func Main anymore.
// See the doc comment on func Main and use MainStart instead.
var errMain = errors.New("testing: unexpected use of func Main")

type matchStringOnly func(pat, str string) (bool, error)

func (f matchStringOnly) MatchString(pat, str string) (bool, error)   { return f(pat, str) }
func (f matchStringOnly) StartCPUProfile(w io.Writer) error           { return errMain }
func (f matchStringOnly) StopCPUProfile()                             {}
func (f matchStringOnly) WriteHeapProfile(w io.Writer) error          { return errMain }
func (f matchStringOnly) WriteProfileTo(string, io.Writer, int) error { return errMain }
func (f matchStringOnly) ImportPath() string                          { return "" }
func (f matchStringOnly) StartTestLog(io.Writer)                      {}
func (f matchStringOnly) StopTestLog() error                          { return errMain }

// Main is an internal function, part of the implementation of the "go test" command.
// It was exported because it is cross-package and predates "internal" packages.
// It is no longer used by "go test" but preserved, as much as possible, for other
// systems that simulate "go test" using Main, but Main sometimes cannot be updated as
// new functionality is added to the testing package.
// Systems simulating "go test" should be updated to use MainStart.
func Main(matchString func(pat, str string) (bool, error), tests []InternalTest, benchmarks []InternalBenchmark, examples []InternalExample) {
        os.Exit(MainStart(matchStringOnly(matchString), tests, benchmarks, examples).Run())
}

// M is a type passed to a TestMain function to run the actual tests.
type M struct {
        deps       testDeps
        tests      []InternalTest
        benchmarks []InternalBenchmark
        examples   []InternalExample

        timer     *time.Timer
        afterOnce sync.Once

        numRun int
}

// testDeps is an internal interface of functionality that is
// passed into this package by a test's generated main package.
// The canonical implementation of this interface is
// testing/internal/testdeps's TestDeps.
type testDeps interface {
        ImportPath() string
        MatchString(pat, str string) (bool, error)
        StartCPUProfile(io.Writer) error
        StopCPUProfile()
        StartTestLog(io.Writer)
        StopTestLog() error
        WriteHeapProfile(io.Writer) error
        WriteProfileTo(string, io.Writer, int) error
}

// MainStart is meant for use by tests generated by 'go test'.
// It is not meant to be called directly and is not subject to the Go 1 compatibility document.
// It may change signature from release to release.
func MainStart(deps testDeps, tests []InternalTest, benchmarks []InternalBenchmark, examples []InternalExample) *M {
        return &M{
                deps:       deps,
                tests:      tests,
                benchmarks: benchmarks,
                examples:   examples,
        }
}

// Run runs the tests. It returns an exit code to pass to os.Exit.
func (m *M) Run() int {
        // Count the number of calls to m.Run.
        // We only ever expected 1, but we didn't enforce that,
        // and now there are tests in the wild that call m.Run multiple times.
        // Sigh. golang.org/issue/23129.
        m.numRun++

        // TestMain may have already called flag.Parse.
        if !flag.Parsed() {
                flag.Parse()
        }

        if *parallel < 1 {
                fmt.Fprintln(os.Stderr, "testing: -parallel can only be given a positive integer")
                flag.Usage()
                return 2
        }

        if len(*matchList) != 0 {
                listTests(m.deps.MatchString, m.tests, m.benchmarks, m.examples)
                return 0
        }

        parseCpuList()

        m.before()
        defer m.after()
        m.startAlarm()
        haveExamples = len(m.examples) > 0
        testRan, testOk := runTests(m.deps.MatchString, m.tests)
        exampleRan, exampleOk := runExamples(m.deps.MatchString, m.examples)
        m.stopAlarm()
        if !testRan && !exampleRan && *matchBenchmarks == "" {
                fmt.Fprintln(os.Stderr, "testing: warning: no tests to run")
        }
        if !testOk || !exampleOk || !runBenchmarks(m.deps.ImportPath(), m.deps.MatchString, m.benchmarks) || race.Errors() > 0 {
                fmt.Println("FAIL")
                return 1
        }

        fmt.Println("PASS")
        return 0
}

func (t *T) report() {
        if t.parent == nil {
                return
        }
        dstr := fmtDuration(t.duration)
        format := "--- %s: %s (%s)\n"
        if t.Failed() {
                t.flushToParent(format, "FAIL", t.name, dstr)
        } else if t.chatty {
                if t.Skipped() {
                        t.flushToParent(format, "SKIP", t.name, dstr)
                } else {
                        t.flushToParent(format, "PASS", t.name, dstr)
                }
        }
}

func listTests(matchString func(pat, str string) (bool, error), tests []InternalTest, benchmarks []InternalBenchmark, examples []InternalExample) {
        if _, err := matchString(*matchList, "non-empty"); err != nil {
                fmt.Fprintf(os.Stderr, "testing: invalid regexp in -test.list (%q): %s\n", *matchList, err)
                os.Exit(1)
        }

        for _, test := range tests {
                if ok, _ := matchString(*matchList, test.Name); ok {
                        fmt.Println(test.Name)
                }
        }
        for _, bench := range benchmarks {
                if ok, _ := matchString(*matchList, bench.Name); ok {
                        fmt.Println(bench.Name)
                }
        }
        for _, example := range examples {
                if ok, _ := matchString(*matchList, example.Name); ok {
                        fmt.Println(example.Name)
                }
        }
}

// An internal function but exported because it is cross-package; part of the implementation
// of the "go test" command.
func RunTests(matchString func(pat, str string) (bool, error), tests []InternalTest) (ok bool) {
        ran, ok := runTests(matchString, tests)
        if !ran && !haveExamples {
                fmt.Fprintln(os.Stderr, "testing: warning: no tests to run")
        }
        return ok
}

func runTests(matchString func(pat, str string) (bool, error), tests []InternalTest) (ran, ok bool) {
        ok = true
        for _, procs := range cpuList {
                runtime.GOMAXPROCS(procs)
                for i := uint(0); i < *count; i++ {
                        if shouldFailFast() {
                                break
                        }
                        ctx := newTestContext(*parallel, newMatcher(matchString, *match, "-test.run"))
                        t := &T{
                                common: common{
                                        signal:  make(chan bool),
                                        barrier: make(chan bool),
                                        w:       os.Stdout,
                                        chatty:  *chatty,
                                },
                                context: ctx,
                        }
                        tRunner(t, func(t *T) {
                                for _, test := range tests {
                                        t.Run(test.Name, test.F)
                                }
                                // Run catching the signal rather than the tRunner as a separate
                                // goroutine to avoid adding a goroutine during the sequential
                                // phase as this pollutes the stacktrace output when aborting.
                                go func() { <-t.signal }()
                        })
                        ok = ok && !t.Failed()
                        ran = ran || t.ran
                }
        }
        return ran, ok
}

// before runs before all testing.
func (m *M) before() {
        if *memProfileRate > 0 {
                runtime.MemProfileRate = *memProfileRate
        }
        if *cpuProfile != "" {
                f, err := os.Create(toOutputDir(*cpuProfile))
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s\n", err)
                        return
                }
                if err := m.deps.StartCPUProfile(f); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't start cpu profile: %s\n", err)
                        f.Close()
                        return
                }
                // Could save f so after can call f.Close; not worth the effort.
        }
        if *traceFile != "" {
                f, err := os.Create(toOutputDir(*traceFile))
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s\n", err)
                        return
                }
                if err := trace.Start(f); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't start tracing: %s\n", err)
                        f.Close()
                        return
                }
                // Could save f so after can call f.Close; not worth the effort.
        }
        if *blockProfile != "" && *blockProfileRate >= 0 {
                runtime.SetBlockProfileRate(*blockProfileRate)
        }
        if *mutexProfile != "" && *mutexProfileFraction >= 0 {
                runtime.SetMutexProfileFraction(*mutexProfileFraction)
        }
        if *coverProfile != "" && cover.Mode == "" {
                fmt.Fprintf(os.Stderr, "testing: cannot use -test.coverprofile because test binary was not built with coverage enabled\n")
                os.Exit(2)
        }
        if *testlog != "" {
                // Note: Not using toOutputDir.
                // This file is for use by cmd/go, not users.
                var f *os.File
                var err error
                if m.numRun == 1 {
                        f, err = os.Create(*testlog)
                } else {
                        f, err = os.OpenFile(*testlog, os.O_WRONLY, 0)
                        if err == nil {
                                f.Seek(0, io.SeekEnd)
                        }
                }
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s\n", err)
                        os.Exit(2)
                }
                m.deps.StartTestLog(f)
                testlogFile = f
        }
}

// after runs after all testing.
func (m *M) after() {
        m.afterOnce.Do(func() {
                m.writeProfiles()
        })
}

func (m *M) writeProfiles() {
        if *testlog != "" {
                if err := m.deps.StopTestLog(); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't write %s: %s\n", *testlog, err)
                        os.Exit(2)
                }
                if err := testlogFile.Close(); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't write %s: %s\n", *testlog, err)
                        os.Exit(2)
                }
        }
        if *cpuProfile != "" {
                m.deps.StopCPUProfile() // flushes profile to disk
        }
        if *traceFile != "" {
                // trace.Stop() // flushes trace to disk
        }
        if *memProfile != "" {
                f, err := os.Create(toOutputDir(*memProfile))
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s\n", err)
                        os.Exit(2)
                }
                runtime.GC() // materialize all statistics
                if err = m.deps.WriteHeapProfile(f); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't write %s: %s\n", *memProfile, err)
                        os.Exit(2)
                }
                f.Close()
        }
        if *blockProfile != "" && *blockProfileRate >= 0 {
                f, err := os.Create(toOutputDir(*blockProfile))
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s\n", err)
                        os.Exit(2)
                }
                if err = m.deps.WriteProfileTo("block", f, 0); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't write %s: %s\n", *blockProfile, err)
                        os.Exit(2)
                }
                f.Close()
        }
        if *mutexProfile != "" && *mutexProfileFraction >= 0 {
                f, err := os.Create(toOutputDir(*mutexProfile))
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s\n", err)
                        os.Exit(2)
                }
                if err = m.deps.WriteProfileTo("mutex", f, 0); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't write %s: %s\n", *blockProfile, err)
                        os.Exit(2)
                }
                f.Close()
        }
        if cover.Mode != "" {
                coverReport()
        }
}

// toOutputDir returns the file name relocated, if required, to outputDir.
// Simple implementation to avoid pulling in path/filepath.
func toOutputDir(path string) string {
        if *outputDir == "" || path == "" {
                return path
        }
        if runtime.GOOS == "windows" {
                // On Windows, it's clumsy, but we can be almost always correct
                // by just looking for a drive letter and a colon.
                // Absolute paths always have a drive letter (ignoring UNC).
                // Problem: if path == "C:A" and outputdir == "C:\Go" it's unclear
                // what to do, but even then path/filepath doesn't help.
                // TODO: Worth doing better? Probably not, because we're here only
                // under the management of go test.
                if len(path) >= 2 {
                        letter, colon := path[0], path[1]
                        if ('a' <= letter && letter <= 'z' || 'A' <= letter && letter <= 'Z') && colon == ':' {
                                // If path starts with a drive letter we're stuck with it regardless.
                                return path
                        }
                }
        }
        if os.IsPathSeparator(path[0]) {
                return path
        }
        return fmt.Sprintf("%s%c%s", *outputDir, os.PathSeparator, path)
}

// startAlarm starts an alarm if requested.
func (m *M) startAlarm() {
        if *timeout > 0 {
                m.timer = time.AfterFunc(*timeout, func() {
                        m.after()
                        debug.SetTraceback("all")
                        panic(fmt.Sprintf("test timed out after %v", *timeout))
                })
        }
}

// stopAlarm turns off the alarm.
func (m *M) stopAlarm() {
        if *timeout > 0 {
                m.timer.Stop()
        }
}

func parseCpuList() {
        for _, val := range strings.Split(*cpuListStr, ",") {
                val = strings.TrimSpace(val)
                if val == "" {
                        continue
                }
                cpu, err := strconv.Atoi(val)
                if err != nil || cpu <= 0 {
                        fmt.Fprintf(os.Stderr, "testing: invalid value %q for -test.cpu\n", val)
                        os.Exit(1)
                }
                cpuList = append(cpuList, cpu)
        }
        if cpuList == nil {
                cpuList = append(cpuList, runtime.GOMAXPROCS(-1))
        }
}

func shouldFailFast() bool {
        return *failFast && atomic.LoadUint32(&numFailed) > 0
}