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engine.go
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// Copyright 2019 Gregory Petrosyan <gregory.petrosyan@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
package rapid
import (
"bytes"
"encoding/binary"
"flag"
"fmt"
"log"
"os"
"path/filepath"
"regexp"
"runtime"
"strings"
"sync"
"testing"
"time"
)
const (
small = 5
invalidChecksMult = 10
exampleMaxTries = 1000
maxTestTimeout = 24 * time.Hour
shrinkStepBound = 10 * time.Second // can be improved by taking average checkOnce runtime into account
tracebackLen = 32
tracebackStop = "pgregory.net/rapid.checkOnce"
runtimePrefix = "runtime."
)
var (
flags cmdline
tracebackBlacklist = map[string]bool{
"pgregory.net/rapid.(*customGen[...]).maybeValue.func1": true,
"pgregory.net/rapid.runAction.func1": true,
}
)
type cmdline struct {
checks int
steps int
failfile string
nofailfile bool
seed uint64
log bool
verbose bool
debug bool
debugvis bool
shrinkTime time.Duration
}
func init() {
flag.IntVar(&flags.checks, "rapid.checks", 100, "rapid: number of checks to perform")
flag.IntVar(&flags.steps, "rapid.steps", 30, "rapid: average number of Repeat actions to execute")
flag.StringVar(&flags.failfile, "rapid.failfile", "", "rapid: fail file to use to reproduce test failure")
flag.BoolVar(&flags.nofailfile, "rapid.nofailfile", false, "rapid: do not write fail files on test failures")
flag.Uint64Var(&flags.seed, "rapid.seed", 0, "rapid: PRNG seed to start with (0 to use a random one)")
flag.BoolVar(&flags.log, "rapid.log", false, "rapid: eager verbose output to stdout (to aid with unrecoverable test failures)")
flag.BoolVar(&flags.verbose, "rapid.v", false, "rapid: verbose output")
flag.BoolVar(&flags.debug, "rapid.debug", false, "rapid: debugging output")
flag.BoolVar(&flags.debugvis, "rapid.debugvis", false, "rapid: debugging visualization")
flag.DurationVar(&flags.shrinkTime, "rapid.shrinktime", 30*time.Second, "rapid: maximum time to spend on test case minimization")
}
func assert(ok bool) {
if !ok {
panic("assertion failed")
}
}
func assertf(ok bool, format string, args ...any) {
if !ok {
panic(fmt.Sprintf(format, args...))
}
}
func assertValidRange(min int, max int) {
if max >= 0 && min > max {
panic(fmt.Sprintf("invalid range [%d, %d]", min, max))
}
}
func checkDeadline(t *testing.T) time.Time {
if t == nil {
return time.Now().Add(maxTestTimeout) // convenience
}
d, ok := t.Deadline()
if !ok {
return time.Now().Add(maxTestTimeout)
}
return d
}
func shrinkDeadline(deadline time.Time) time.Time {
d := time.Now().Add(flags.shrinkTime)
max := deadline.Add(-shrinkStepBound) // account for the fact that shrink deadline is checked before the step
if d.After(max) {
d = max
}
return d
}
// Check fails the current test if rapid can find a test case which falsifies prop.
//
// Property is falsified in case of a panic or a call to
// [*T.Fatalf], [*T.Fatal], [*T.Errorf], [*T.Error], [*T.FailNow] or [*T.Fail].
func Check(t *testing.T, prop func(*T)) {
t.Helper()
checkTB(t, checkDeadline(t), prop)
}
// MakeCheck is a convenience function for defining subtests suitable for
// [*testing.T.Run]. It allows you to write this:
//
// t.Run("subtest name", rapid.MakeCheck(func(t *rapid.T) {
// // test code
// }))
//
// instead of this:
//
// t.Run("subtest name", func(t *testing.T) {
// rapid.Check(t, func(t *rapid.T) {
// // test code
// })
// })
func MakeCheck(prop func(*T)) func(*testing.T) {
return func(t *testing.T) {
t.Helper()
checkTB(t, checkDeadline(t), prop)
}
}
// MakeFuzz creates a fuzz target for [*testing.F.Fuzz]:
//
// func FuzzFoo(f *testing.F) {
// f.Fuzz(rapid.MakeFuzz(func(t *rapid.T) {
// // test code
// }))
// }
func MakeFuzz(prop func(*T)) func(*testing.T, []byte) {
return func(t *testing.T, input []byte) {
t.Helper()
checkFuzz(t, prop, input)
}
}
func checkFuzz(tb tb, prop func(*T), input []byte) {
tb.Helper()
var buf []uint64
for len(input) > 0 {
var tmp [8]byte
n := copy(tmp[:], input)
buf = append(buf, binary.LittleEndian.Uint64(tmp[:]))
input = input[n:]
}
t := newT(tb, newBufBitStream(buf, false), true, nil)
err := checkOnce(t, prop)
switch {
case err == nil:
// do nothing
case err.isInvalidData():
tb.SkipNow()
case err.isStopTest():
tb.Fatalf("[rapid] failed: %v", err)
default:
tb.Fatalf("[rapid] panic: %v\nTraceback:\n%v", err, traceback(err))
}
}
func checkTB(tb tb, deadline time.Time, prop func(*T)) {
tb.Helper()
checks := flags.checks
if testing.Short() {
checks /= 5
}
start := time.Now()
valid, invalid, earlyExit, seed, failfile, buf, err1, err2 := doCheck(tb, deadline, checks, baseSeed(), flags.failfile, true, prop)
dt := time.Since(start)
if err1 == nil && err2 == nil {
if valid == checks || (earlyExit && valid > 0) {
tb.Logf("[rapid] OK, passed %v tests (%v)", valid, dt)
} else {
tb.Errorf("[rapid] only generated %v valid tests from %v total (%v)", valid, valid+invalid, dt)
}
} else {
if failfile == "" && !flags.nofailfile {
_, failfile = failFileName(tb.Name())
out := captureTestOutput(tb, prop, buf)
err := saveFailFile(failfile, rapidVersion, out, seed, buf)
if err != nil {
tb.Logf("[rapid] %v", err)
failfile = ""
}
}
var repr string
switch {
case failfile != "" && seed != 0:
repr = fmt.Sprintf("-rapid.failfile=%q (or -rapid.seed=%d)", failfile, seed)
case failfile != "":
repr = fmt.Sprintf("-rapid.failfile=%q", failfile)
case seed != 0:
repr = fmt.Sprintf("-rapid.seed=%d", seed)
}
name := regexp.QuoteMeta(tb.Name())
if traceback(err1) == traceback(err2) {
if err2.isStopTest() {
tb.Errorf("[rapid] failed after %v tests: %v\nTo reproduce, specify -run=%q %v\nFailed test output:", valid, err2, name, repr)
} else {
tb.Errorf("[rapid] panic after %v tests: %v\nTo reproduce, specify -run=%q %v\nTraceback:\n%vFailed test output:", valid, err2, name, repr, traceback(err2))
}
} else {
tb.Errorf("[rapid] flaky test, can not reproduce a failure\nTo try to reproduce, specify -run=%q %v\nTraceback (%v):\n%vOriginal traceback (%v):\n%vFailed test output:", name, repr, err2, traceback(err2), err1, traceback(err1))
}
_ = checkOnce(newT(tb, newBufBitStream(buf, false), true, nil), prop) // output using (*testing.T).Log for proper line numbers
}
if tb.Failed() {
tb.FailNow() // do not try to run any checks after the first failed one
}
}
func doCheck(tb tb, deadline time.Time, checks int, seed uint64, failfile string, globFailFiles bool, prop func(*T)) (int, int, bool, uint64, string, []uint64, *testError, *testError) {
tb.Helper()
assertf(!tb.Failed(), "check function called with *testing.T which has already failed")
var failfiles []string
if failfile != "" {
failfiles = []string{failfile}
}
if globFailFiles {
matches, _ := filepath.Glob(failFilePattern(tb.Name()))
failfiles = append(failfiles, matches...)
}
for _, failfile := range failfiles {
buf, err1, err2 := checkFailFile(tb, failfile, prop)
if err1 != nil || err2 != nil {
return 0, 0, false, 0, failfile, buf, err1, err2
}
}
valid, invalid, earlyExit, seed, err1 := findBug(tb, deadline, checks, seed, prop)
if err1 == nil {
return valid, invalid, earlyExit, 0, "", nil, nil, nil
}
s := newRandomBitStream(seed, true)
t := newT(tb, s, flags.verbose, nil)
t.Logf("[rapid] trying to reproduce the failure")
err2 := checkOnce(t, prop)
if !sameError(err1, err2) {
return valid, invalid, false, seed, "", s.data, err1, err2
}
t.Logf("[rapid] trying to minimize the failing test case")
buf, err3 := shrink(tb, shrinkDeadline(deadline), s.recordedBits, err2, prop)
return valid, invalid, false, seed, "", buf, err2, err3
}
func checkFailFile(tb tb, failfile string, prop func(*T)) ([]uint64, *testError, *testError) {
tb.Helper()
version, _, buf, err := loadFailFile(failfile)
if err != nil {
tb.Logf("[rapid] ignoring fail file: %v", err)
return nil, nil, nil
}
if version != rapidVersion {
tb.Logf("[rapid] ignoring fail file: version %q differs from rapid version %q", version, rapidVersion)
return nil, nil, nil
}
s1 := newBufBitStream(buf, false)
t1 := newT(tb, s1, flags.verbose, nil)
err1 := checkOnce(t1, prop)
if err1 == nil {
return nil, nil, nil
}
if err1.isInvalidData() {
tb.Logf("[rapid] fail file %q is no longer valid", failfile)
return nil, nil, nil
}
s2 := newBufBitStream(buf, false)
t2 := newT(tb, s2, flags.verbose, nil)
t2.Logf("[rapid] trying to reproduce the failure")
err2 := checkOnce(t2, prop)
return buf, err1, err2
}
func findBug(tb tb, deadline time.Time, checks int, seed uint64, prop func(*T)) (int, int, bool, uint64, *testError) {
tb.Helper()
var (
r = newRandomBitStream(0, false)
t = newT(tb, r, flags.verbose, nil)
valid = 0
invalid = 0
)
var total time.Duration
for valid < checks && invalid < checks*invalidChecksMult {
iter := valid + invalid
if iter > 0 && time.Until(deadline) < total/time.Duration(iter)*5 {
if t.shouldLog() {
t.Logf("[rapid] early exit after test #%v (%v)", iter, total)
}
return valid, invalid, true, 0, nil
}
seed += uint64(iter)
r.init(seed)
start := time.Now()
if t.shouldLog() {
t.Logf("[rapid] test #%v start (seed %v)", iter+1, seed)
}
err := checkOnce(t, prop)
dt := time.Since(start)
total += dt
if err == nil {
if t.shouldLog() {
t.Logf("[rapid] test #%v OK (%v)", iter+1, dt)
}
valid++
} else if err.isInvalidData() {
if t.shouldLog() {
t.Logf("[rapid] test #%v invalid (%v)", iter+1, dt)
}
invalid++
} else {
if t.shouldLog() {
t.Logf("[rapid] test #%v failed: %v", iter+1, err)
}
return valid, invalid, false, seed, err
}
}
return valid, invalid, false, 0, nil
}
func checkOnce(t *T, prop func(*T)) (err *testError) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
defer func() { err = panicToError(recover(), 3) }()
prop(t)
t.failOnError()
return nil
}
func captureTestOutput(tb tb, prop func(*T), buf []uint64) []byte {
var b bytes.Buffer
l := log.New(&b, fmt.Sprintf("[%v] ", tb.Name()), log.Lmsgprefix|log.Ldate|log.Ltime|log.Lmicroseconds)
_ = checkOnce(newT(tb, newBufBitStream(buf, false), false, l), prop)
return b.Bytes()
}
type invalidData string
type stopTest string
type testError struct {
data any
traceback string
}
func panicToError(p any, skip int) *testError {
if p == nil {
return nil
}
callers := make([]uintptr, tracebackLen)
callers = callers[:runtime.Callers(skip, callers)]
frames := runtime.CallersFrames(callers)
b := &strings.Builder{}
f, more, skipSpecial := runtime.Frame{}, true, true
for more && !strings.HasSuffix(f.Function, tracebackStop) {
f, more = frames.Next()
if skipSpecial && (tracebackBlacklist[f.Function] || strings.HasPrefix(f.Function, runtimePrefix)) {
continue
}
skipSpecial = false
_, err := fmt.Fprintf(b, " %s:%d in %s\n", f.File, f.Line, f.Function)
assert(err == nil)
}
return &testError{
data: p,
traceback: b.String(),
}
}
func (err *testError) Error() string {
if msg, ok := err.data.(stopTest); ok {
return string(msg)
}
if msg, ok := err.data.(invalidData); ok {
return fmt.Sprintf("invalid data: %s", string(msg))
}
return fmt.Sprintf("%v", err.data)
}
func (err *testError) isInvalidData() bool {
_, ok := err.data.(invalidData)
return ok
}
func (err *testError) isStopTest() bool {
_, ok := err.data.(stopTest)
return ok
}
func sameError(err1 *testError, err2 *testError) bool {
return errorString(err1) == errorString(err2) && traceback(err1) == traceback(err2)
}
func errorString(err *testError) string {
if err == nil {
return ""
}
return err.Error()
}
func traceback(err *testError) string {
if err == nil {
return " <no error>\n"
}
return err.traceback
}
// TB is a common interface between [*testing.T], [*testing.B] and [*T].
type TB interface {
Helper()
Name() string
Logf(format string, args ...any)
Log(args ...any)
Skipf(format string, args ...any)
Skip(args ...any)
SkipNow()
Errorf(format string, args ...any)
Error(args ...any)
Fatalf(format string, args ...any)
Fatal(args ...any)
FailNow()
Fail()
Failed() bool
}
// tb is a private copy of TB, made to avoid T having public fields
type tb interface {
Helper()
Name() string
Logf(format string, args ...any)
Log(args ...any)
Skipf(format string, args ...any)
Skip(args ...any)
SkipNow()
Errorf(format string, args ...any)
Error(args ...any)
Fatalf(format string, args ...any)
Fatal(args ...any)
FailNow()
Fail()
Failed() bool
}
// T is similar to [testing.T], but with extra bookkeeping for property-based tests.
//
// For tests to be reproducible, they should generally run in a single goroutine.
// If concurrency is unavoidable, methods on *T, such as [*testing.T.Helper] and [*T.Errorf],
// are safe for concurrent calls, but *Generator.Draw from a given *T is not.
type T struct {
tb // unnamed to force re-export of (*T).Helper()
tbLog bool
rawLog *log.Logger
s bitStream
draws int
refDraws []any
mu sync.RWMutex
failed stopTest
}
func newT(tb tb, s bitStream, tbLog bool, rawLog *log.Logger, refDraws ...any) *T {
t := &T{
tb: tb,
tbLog: tbLog,
rawLog: rawLog,
s: s,
refDraws: refDraws,
}
if rawLog == nil && flags.log {
testName := "rapid test"
if tb != nil {
testName = tb.Name()
}
t.rawLog = log.New(os.Stdout, fmt.Sprintf("[%v] ", testName), log.Lmsgprefix|log.Ldate|log.Ltime|log.Lmicroseconds)
}
return t
}
func (t *T) shouldLog() bool {
return t.rawLog != nil || (t.tbLog && t.tb != nil)
}
func (t *T) Logf(format string, args ...any) {
if t.rawLog != nil {
t.rawLog.Printf(format, args...)
} else if t.tbLog && t.tb != nil {
t.tb.Helper()
t.tb.Logf(format, args...)
}
}
func (t *T) Log(args ...any) {
if t.rawLog != nil {
t.rawLog.Print(args...)
} else if t.tbLog && t.tb != nil {
t.tb.Helper()
t.tb.Log(args...)
}
}
// Skipf is equivalent to [T.Logf] followed by [T.SkipNow].
func (t *T) Skipf(format string, args ...any) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
t.Logf(format, args...)
t.skip(fmt.Sprintf(format, args...))
}
// Skip is equivalent to [T.Log] followed by [T.SkipNow].
func (t *T) Skip(args ...any) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
t.Log(args...)
t.skip(fmt.Sprint(args...))
}
// SkipNow marks the current test case as invalid (except in [T.Repeat]
// actions, where it marks current action as non-applicable instead).
// If too many test cases are skipped, rapid will mark the test as failing
// due to inability to generate enough valid test cases.
//
// Prefer *Generator.Filter to SkipNow, and prefer generators that always produce
// valid test cases to Filter.
func (t *T) SkipNow() {
t.skip("(*T).SkipNow() called")
}
// Errorf is equivalent to [T.Logf] followed by [T.Fail].
func (t *T) Errorf(format string, args ...any) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
t.Logf(format, args...)
t.fail(false, fmt.Sprintf(format, args...))
}
// Error is equivalent to [T.Log] followed by [T.Fail].
func (t *T) Error(args ...any) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
t.Log(args...)
t.fail(false, fmt.Sprint(args...))
}
// Fatalf is equivalent to [T.Logf] followed by [T.FailNow].
func (t *T) Fatalf(format string, args ...any) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
t.Logf(format, args...)
t.fail(true, fmt.Sprintf(format, args...))
}
// Fatal is equivalent to [T.Log] followed by [T.FailNow].
func (t *T) Fatal(args ...any) {
if t.tbLog && t.tb != nil {
t.tb.Helper()
}
t.Log(args...)
t.fail(true, fmt.Sprint(args...))
}
func (t *T) FailNow() {
t.fail(true, "(*T).FailNow() called")
}
func (t *T) Fail() {
t.fail(false, "(*T).Fail() called")
}
func (t *T) Failed() bool {
t.mu.RLock()
defer t.mu.RUnlock()
return t.failed != ""
}
func (t *T) skip(msg string) {
panic(invalidData(msg))
}
func (t *T) fail(now bool, msg string) {
t.mu.Lock()
defer t.mu.Unlock()
t.failed = stopTest(msg)
if now {
panic(t.failed)
}
}
func (t *T) failOnError() {
t.mu.RLock()
defer t.mu.RUnlock()
if t.failed != "" {
panic(t.failed)
}
}