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// 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 can be any alphanumeric string (but the first letter must not be in
// [a-z]) and serves to identify the test routine.
// These TestXxx routines should be declared within the package they are testing.
//
// Functions of the form
//     func BenchmarkXxx(*testing.B)
// are considered benchmarks, and are executed by gotest when the -test.bench
// flag is provided.
//
// A sample benchmark function looks like this:
//     func BenchmarkHello(b *testing.B) {
//         for i := 0; i < b.N; i++ {
//             fmt.Sprintf("hello")
//         }
//     }
//
// The benchmark package will vary b.N until the benchmark function lasts
// long enough to be timed reliably.  The output
//     testing.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 stopped:
//     func BenchmarkBigLen(b *testing.B) {
//         b.StopTimer()
//         big := NewBig()
//         b.StartTimer()
//         for i := 0; i < b.N; i++ {
//             big.Len()
//         }
//     }
//
// The package also runs and verifies example code. Example functions
// include an introductory comment that is compared with the standard output
// of the function when the tests are run, as in this example of an example:
//
//     // hello
//     func ExampleHello() {
//             fmt.Println("hello")
//     }
//
// Example functions without comments are compiled but not executed.
//
// The naming convention to declare examples for a function F, a type T and
// method M on type T are:
//
//     func ExampleF() { ... }
//     func ExampleT() { ... }
//     func ExampleT_M() { ... }
//
// Multiple example functions for a type/function/method may be provided by
// appending a distinct suffix to the name. The suffix must start with a
// lower-case letter.
//
//     func ExampleF_suffix() { ... }
//     func ExampleT_suffix() { ... }
//     func ExampleT_M_suffix() { ... }
//
package testing

import (
        "flag"
        "fmt"
        "os"
        "runtime"
        "runtime/pprof"
        "strconv"
        "strings"
        "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 "gotest" will do a
        // full test of the package.
        short = flag.Bool("test.short", false, "run smaller test suite to save time")

        // Report as tests are run; default is silent for success.
        chatty         = flag.Bool("test.v", false, "verbose: print additional output")
        match          = flag.String("test.run", "", "regular expression to select tests to run")
        memProfile     = flag.String("test.memprofile", "", "write a memory profile to the named file after execution")
        memProfileRate = flag.Int("test.memprofilerate", 0, "if >=0, sets runtime.MemProfileRate")
        cpuProfile     = flag.String("test.cpuprofile", "", "write a cpu profile to the named file during execution")
        timeout        = flag.Duration("test.timeout", 0, "if positive, sets an aggregate time limit for all tests")
        cpuListStr     = flag.String("test.cpu", "", "comma-separated list of number of CPUs to use for each test")
        parallel       = flag.Int("test.parallel", runtime.GOMAXPROCS(0), "maximum test parallelism")

        cpuList []int
)

// common holds the elements common between T and B and
// captures common methods such as Errorf.
type common struct {
        output   []byte    // Output generated by test or benchmark.
        failed   bool      // Test or benchmark has failed.
        start    time.Time // Time test or benchmark started
        duration time.Duration
        self     interface{}      // To be sent on signal channel when done.
        signal   chan interface{} // Output for serial tests.
}

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

// decorate inserts the final newline if needed and indentation tabs for formatting.
// If addFileLine is true, it also prefixes the string with the file and line of the call site.
func decorate(s string, addFileLine bool) string {
        if addFileLine {
                _, file, line, ok := runtime.Caller(3) // decorate + log + public function.
                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
                }
                s = fmt.Sprintf("%s:%d: %s", file, line, s)
        }
        s = "\t" + s // Every line is indented at least one tab.
        n := len(s)
        if n > 0 && s[n-1] != '\n' {
                s += "\n"
                n++
        }
        for i := 0; i < n-1; i++ { // -1 to avoid final newline
                if s[i] == '\n' {
                        // Second and subsequent lines are indented an extra tab.
                        return s[0:i+1] + "\t" + decorate(s[i+1:n], false)
                }
        }
        return s
}

// 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 error when done.
type T struct {
        common
        name          string    // Name of test.
        startParallel chan bool // Parallel tests will wait on this.
}

// Fail marks the function as having failed but continues execution.
func (c *common) Fail() { c.failed = true }

// Failed returns whether the function has failed.
func (c *common) Failed() bool { return c.failed }

// FailNow marks the function as having failed and stops its execution.
// Execution will continue at the next Test.
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.
        runtime.Goexit()
}

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

// Log formats its arguments using default formatting, analogous to Println(),
// and records the text in the error log.
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.
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()
}

// TODO(dsymonds): Consider hooking into runtime·traceback instead.
func (c *common) stack() {
        for i := 2; ; i++ { // Caller we care about is the user, 2 frames up
                pc, file, line, ok := runtime.Caller(i)
                f := runtime.FuncForPC(pc)
                if !ok || f == nil {
                        break
                }
                c.Logf("%s:%d (0x%x)", file, line, pc)
                c.Logf("\t%s", f.Name())
        }
}

// Parallel signals that this test is to be run in parallel with (and only with) 
// other parallel tests in this CPU group.
func (t *T) Parallel() {
        t.signal <- (*T)(nil) // Release main testing loop
        <-t.startParallel     // Wait for serial tests to finish
}

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

func tRunner(t *T, test *InternalTest) {
        t.start = time.Now()

        // When this goroutine is done, either because test.F(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() {
                // Consider any uncaught panic a failure.
                if err := recover(); err != nil {
                        t.failed = true
                        t.Log(err)
                        t.stack()
                }

                t.duration = time.Now().Sub(t.start)
                t.signal <- t
        }()

        test.F(t)
}

// An internal function but exported because it is cross-package; part of the implementation
// of gotest.
func Main(matchString func(pat, str string) (bool, error), tests []InternalTest, benchmarks []InternalBenchmark, examples []InternalExample) {
        flag.Parse()
        parseCpuList()

        before()
        startAlarm()
        testOk := RunTests(matchString, tests)
        exampleOk := RunExamples(examples)
        if !testOk || !exampleOk {
                fmt.Println("FAIL")
                os.Exit(1)
        }
        fmt.Println("PASS")
        stopAlarm()
        RunBenchmarks(matchString, benchmarks)
        after()
}

func (t *T) report() {
        tstr := fmt.Sprintf("(%.2f seconds)", t.duration.Seconds())
        format := "--- %s: %s %s\n%s"
        if t.failed {
                fmt.Printf(format, "FAIL", t.name, tstr, t.output)
        } else if *chatty {
                fmt.Printf(format, "PASS", t.name, tstr, t.output)
        }
}

func RunTests(matchString func(pat, str string) (bool, error), tests []InternalTest) (ok bool) {
        ok = true
        if len(tests) == 0 {
                fmt.Fprintln(os.Stderr, "testing: warning: no tests to run")
                return
        }
        for _, procs := range cpuList {
                runtime.GOMAXPROCS(procs)
                // We build a new channel tree for each run of the loop.
                // collector merges in one channel all the upstream signals from parallel tests.
                // If all tests pump to the same channel, a bug can occur where a test
                // kicks off a goroutine that Fails, yet the test still delivers a completion signal,
                // which skews the counting.
                var collector = make(chan interface{})

                numParallel := 0
                startParallel := make(chan bool)

                for i := 0; i < len(tests); i++ {
                        matched, err := matchString(*match, tests[i].Name)
                        if err != nil {
                                fmt.Fprintf(os.Stderr, "testing: invalid regexp for -test.run: %s\n", err)
                                os.Exit(1)
                        }
                        if !matched {
                                continue
                        }
                        testName := tests[i].Name
                        if procs != 1 {
                                testName = fmt.Sprintf("%s-%d", tests[i].Name, procs)
                        }
                        t := &T{
                                common: common{
                                        signal: make(chan interface{}),
                                },
                                name:          testName,
                                startParallel: startParallel,
                        }
                        t.self = t
                        if *chatty {
                                fmt.Printf("=== RUN %s\n", t.name)
                        }
                        go tRunner(t, &tests[i])
                        out := (<-t.signal).(*T)
                        if out == nil { // Parallel run.
                                go func() {
                                        collector <- <-t.signal
                                }()
                                numParallel++
                                continue
                        }
                        t.report()
                        ok = ok && !out.failed
                }

                running := 0
                for numParallel+running > 0 {
                        if running < *parallel && numParallel > 0 {
                                startParallel <- true
                                running++
                                numParallel--
                                continue
                        }
                        t := (<-collector).(*T)
                        t.report()
                        ok = ok && !t.failed
                        running--
                }
        }
        return
}

// before runs before all testing.
func before() {
        if *memProfileRate > 0 {
                runtime.MemProfileRate = *memProfileRate
        }
        if *cpuProfile != "" {
                f, err := os.Create(*cpuProfile)
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s", err)
                        return
                }
                if err := pprof.StartCPUProfile(f); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't start cpu profile: %s", err)
                        f.Close()
                        return
                }
                // Could save f so after can call f.Close; not worth the effort.
        }

}

// after runs after all testing.
func after() {
        if *cpuProfile != "" {
                pprof.StopCPUProfile() // flushes profile to disk
        }
        if *memProfile != "" {
                f, err := os.Create(*memProfile)
                if err != nil {
                        fmt.Fprintf(os.Stderr, "testing: %s", err)
                        return
                }
                if err = pprof.WriteHeapProfile(f); err != nil {
                        fmt.Fprintf(os.Stderr, "testing: can't write %s: %s", *memProfile, err)
                }
                f.Close()
        }
}

var timer *time.Timer

// startAlarm starts an alarm if requested.
func startAlarm() {
        if *timeout > 0 {
                timer = time.AfterFunc(*timeout, alarm)
        }
}

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

// alarm is called if the timeout expires.
func alarm() {
        panic("test timed out")
}

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