1 files changed, 259 insertions, 0 deletions
diff --git a/src/runtime/coverage/testdata/harness.go b/src/runtime/coverage/testdata/harness.go
new file mode 100644
index 0000000..5c87e4c
--- /dev/null
+++ b/src/runtime/coverage/testdata/harness.go
@@ -0,0 +1,259 @@
+// Copyright 2022 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 main
+
+import (
+	"flag"
+	"fmt"
+	"internal/coverage/slicewriter"
+	"io"
+	"io/ioutil"
+	"log"
+	"path/filepath"
+	"runtime/coverage"
+	"strings"
+)
+
+var verbflag = flag.Int("v", 0, "Verbose trace output level")
+var testpointflag = flag.String("tp", "", "Testpoint to run")
+var outdirflag = flag.String("o", "", "Output dir into which to emit")
+
+func emitToWriter() {
+	log.SetPrefix("emitToWriter: ")
+	var slwm slicewriter.WriteSeeker
+	if err := coverage.WriteMeta(&slwm); err != nil {
+		log.Fatalf("error: WriteMeta returns %v", err)
+	}
+	mf := filepath.Join(*outdirflag, "covmeta.0abcdef")
+	if err := ioutil.WriteFile(mf, slwm.BytesWritten(), 0666); err != nil {
+		log.Fatalf("error: writing %s: %v", mf, err)
+	}
+	var slwc slicewriter.WriteSeeker
+	if err := coverage.WriteCounters(&slwc); err != nil {
+		log.Fatalf("error: WriteCounters returns %v", err)
+	}
+	cf := filepath.Join(*outdirflag, "covcounters.0abcdef.99.77")
+	if err := ioutil.WriteFile(cf, slwc.BytesWritten(), 0666); err != nil {
+		log.Fatalf("error: writing %s: %v", cf, err)
+	}
+}
+
+func emitToDir() {
+	log.SetPrefix("emitToDir: ")
+	if err := coverage.WriteMetaDir(*outdirflag); err != nil {
+		log.Fatalf("error: WriteMetaDir returns %v", err)
+	}
+	if err := coverage.WriteCountersDir(*outdirflag); err != nil {
+		log.Fatalf("error: WriteCountersDir returns %v", err)
+	}
+}
+
+func emitToNonexistentDir() {
+	log.SetPrefix("emitToNonexistentDir: ")
+
+	want := []string{
+		"no such file or directory",             // linux-ish
+		"system cannot find the file specified", // windows
+		"does not exist",                        // plan9
+	}
+
+	checkWant := func(which string, got string) {
+		found := false
+		for _, w := range want {
+			if strings.Contains(got, w) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			log.Fatalf("%s emit to bad dir: got error:\n  %v\nwanted error with one of:\n  %+v", which, got, want)
+		}
+	}
+
+	// Mangle the output directory to produce something nonexistent.
+	mangled := *outdirflag + "_MANGLED"
+	if err := coverage.WriteMetaDir(mangled); err == nil {
+		log.Fatal("expected error from WriteMetaDir to nonexistent dir")
+	} else {
+		got := fmt.Sprintf("%v", err)
+		checkWant("meta data", got)
+	}
+
+	// Now try to emit counter data file to a bad dir.
+	if err := coverage.WriteCountersDir(mangled); err == nil {
+		log.Fatal("expected error emitting counter data to bad dir")
+	} else {
+		got := fmt.Sprintf("%v", err)
+		checkWant("counter data", got)
+	}
+}
+
+func emitToUnwritableDir() {
+	log.SetPrefix("emitToUnwritableDir: ")
+
+	want := "permission denied"
+
+	if err := coverage.WriteMetaDir(*outdirflag); err == nil {
+		log.Fatal("expected error from WriteMetaDir to unwritable dir")
+	} else {
+		got := fmt.Sprintf("%v", err)
+		if !strings.Contains(got, want) {
+			log.Fatalf("meta-data emit to unwritable dir: wanted error containing %q got %q", want, got)
+		}
+	}
+
+	// Similarly with writing counter data.
+	if err := coverage.WriteCountersDir(*outdirflag); err == nil {
+		log.Fatal("expected error emitting counter data to unwritable dir")
+	} else {
+		got := fmt.Sprintf("%v", err)
+		if !strings.Contains(got, want) {
+			log.Fatalf("emitting counter data to unwritable dir: wanted error containing %q got %q", want, got)
+		}
+	}
+}
+
+func emitToNilWriter() {
+	log.SetPrefix("emitToWriter: ")
+	want := "nil writer"
+	var bad io.WriteSeeker
+	if err := coverage.WriteMeta(bad); err == nil {
+		log.Fatal("expected error passing nil writer for meta emit")
+	} else {
+		got := fmt.Sprintf("%v", err)
+		if !strings.Contains(got, want) {
+			log.Fatalf("emitting meta-data passing nil writer: wanted error containing %q got %q", want, got)
+		}
+	}
+
+	if err := coverage.WriteCounters(bad); err == nil {
+		log.Fatal("expected error passing nil writer for counter emit")
+	} else {
+		got := fmt.Sprintf("%v", err)
+		if !strings.Contains(got, want) {
+			log.Fatalf("emitting counter data passing nil writer: wanted error containing %q got %q", want, got)
+		}
+	}
+}
+
+type failingWriter struct {
+	writeCount int
+	writeLimit int
+	slws       slicewriter.WriteSeeker
+}
+
+func (f *failingWriter) Write(p []byte) (n int, err error) {
+	c := f.writeCount
+	f.writeCount++
+	if f.writeLimit < 0 || c < f.writeLimit {
+		return f.slws.Write(p)
+	}
+	return 0, fmt.Errorf("manufactured write error")
+}
+
+func (f *failingWriter) Seek(offset int64, whence int) (int64, error) {
+	return f.slws.Seek(offset, whence)
+}
+
+func (f *failingWriter) reset(lim int) {
+	f.writeCount = 0
+	f.writeLimit = lim
+	f.slws = slicewriter.WriteSeeker{}
+}
+
+func writeStressTest(tag string, testf func(testf *failingWriter) error) {
+	// Invoke the function initially without the write limit
+	// set, to capture the number of writes performed.
+	fw := &failingWriter{writeLimit: -1}
+	testf(fw)
+
+	// Now that we know how many writes are going to happen, run the
+	// function repeatedly, each time with a Write operation set to
+	// fail at a new spot. The goal here is to make sure that:
+	// A) an error is reported, and B) nothing crashes.
+	tot := fw.writeCount
+	for i := 0; i < tot; i++ {
+		fw.reset(i)
+		err := testf(fw)
+		if err == nil {
+			log.Fatalf("no error from write %d tag %s", i, tag)
+		}
+	}
+}
+
+func postClear() int {
+	return 42
+}
+
+func preClear() int {
+	return 42
+}
+
+// This test is designed to ensure that write errors are properly
+// handled by the code that writes out coverage data. It repeatedly
+// invokes the 'emit to writer' apis using a specially crafted writer
+// that captures the total number of expected writes, then replays the
+// execution N times with a manufactured write error at the
+// appropriate spot.
+func emitToFailingWriter() {
+	log.SetPrefix("emitToFailingWriter: ")
+
+	writeStressTest("emit-meta", func(f *failingWriter) error {
+		return coverage.WriteMeta(f)
+	})
+	writeStressTest("emit-counter", func(f *failingWriter) error {
+		return coverage.WriteCounters(f)
+	})
+}
+
+func emitWithCounterClear() {
+	log.SetPrefix("emitWitCounterClear: ")
+	preClear()
+	if err := coverage.ClearCounters(); err != nil {
+		log.Fatalf("clear failed: %v", err)
+	}
+	postClear()
+	if err := coverage.WriteMetaDir(*outdirflag); err != nil {
+		log.Fatalf("error: WriteMetaDir returns %v", err)
+	}
+	if err := coverage.WriteCountersDir(*outdirflag); err != nil {
+		log.Fatalf("error: WriteCountersDir returns %v", err)
+	}
+}
+
+func final() int {
+	println("I run last.")
+	return 43
+}
+
+func main() {
+	log.SetFlags(0)
+	flag.Parse()
+	if *testpointflag == "" {
+		log.Fatalf("error: no testpoint (use -tp flag)")
+	}
+	if *outdirflag == "" {
+		log.Fatalf("error: no output dir specified (use -o flag)")
+	}
+	switch *testpointflag {
+	case "emitToDir":
+		emitToDir()
+	case "emitToWriter":
+		emitToWriter()
+	case "emitToNonexistentDir":
+		emitToNonexistentDir()
+	case "emitToUnwritableDir":
+		emitToUnwritableDir()
+	case "emitToNilWriter":
+		emitToNilWriter()
+	case "emitToFailingWriter":
+		emitToFailingWriter()
+	case "emitWithCounterClear":
+		emitWithCounterClear()
+	default:
+		log.Fatalf("error: unknown testpoint %q", *testpointflag)
+	}
+	final()
+}