go.tools/cmd/cover: add a test

Test the statistics work as expected for a simple program, which can be extended as needed. This is all a bit meta.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10392050

cmd/cover/cover_test.go

@@ -0,0 +1,87 @@
+// Copyright 2013 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_test
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+const (
+	// Data directory, also the package directory for the test.
+	testdata = "testdata"
+
+	// Binaries we compile.
+	testcover = "testcover.exe"
+)
+
+var (
+	// Files we use.
+	testMain    = filepath.Join(testdata, "main.go")
+	testTest    = filepath.Join(testdata, "test.go")
+	coverInput  = filepath.Join(testdata, "test_line.go")
+	coverOutput = filepath.Join(testdata, "test_cover.go")
+)
+
+var debug = false // Keeps the rewritten files around if set.
+
+// Run this shell script, but do it in Go so it can be run by "go test".
+//
+//	replace the word LINE with the line number < testdata/test.go > testdata/test_line.go
+// 	go build -o ./testcover
+// 	./testcover -mode=count -var=CoverTest -o ./testdata/test_cover.go testdata/test_line.go
+//	go run ./testdata/main.go ./testdata/test.go
+//
+func TestCover(t *testing.T) {
+	// Read in the test file (testTest) and write it, with LINEs specified, to coverInput.
+	file, err := ioutil.ReadFile(testTest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	lines := bytes.Split(file, []byte("\n"))
+	for i, line := range lines {
+		lines[i] = bytes.Replace(line, []byte("LINE"), []byte(fmt.Sprint(i+1)), -1)
+	}
+	err = ioutil.WriteFile(coverInput, bytes.Join(lines, []byte("\n")), 0666)
+
+	// defer removal of test_line_go
+	if !debug {
+		defer os.Remove(coverInput)
+	}
+
+	// go build -o testcover
+	cmd := exec.Command("go", "build", "-o", testcover)
+	run(cmd, t)
+
+	// defer removal of testcover
+	defer os.Remove(testcover)
+
+	// ./testcover -mode=count -var=coverTest -o ./testdata/test_cover.go testdata/test_line.go
+	cmd = exec.Command(testcover, "-mode=count", "-var=coverTest", "-o", coverOutput, coverInput)
+	run(cmd, t)
+
+	// defer removal of ./testdata/test_cover.go
+	if !debug {
+		defer os.Remove(coverOutput)
+	}
+
+	// go run ./testdata/main.go ./testdata/test.go
+	cmd = exec.Command("go", "run", testMain, coverOutput)
+	run(cmd, t)
+}
+
+func run(c *exec.Cmd, t *testing.T) {
+	c.Stdout = os.Stdout
+	c.Stderr = os.Stderr
+	err := c.Run()
+	if err != nil {
+		t.Fatal(err)
+	}
+}

cmd/cover/testdata/main.go

@@ -0,0 +1,64 @@
+// Copyright 2013 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.
+
+// Test runner for coverage test. This file is not coverage-annotated; test.go is.
+// It knows the coverage counter is called "coverTest".
+
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	testAll()
+	verify()
+}
+
+type block struct {
+	count uint32
+	line  uint32
+}
+
+var counters = make(map[block]bool)
+
+// check records the location and expected value for a counter.
+func check(line, count uint32) {
+	b := block{
+		count,
+		line,
+	}
+	counters[b] = true
+}
+
+// verify checks the expected counts against the actual. It runs after the test has completed.
+func verify() {
+	ok := true
+	for b := range counters {
+		got := count(b.line)
+		if b.count == anything && got != 0 {
+			got = anything
+		}
+		if got != b.count {
+			fmt.Fprintf(os.Stderr, "test_go:%d expected count %d got %d\n", b.line, b.count, got)
+			ok = false
+		}
+	}
+	if !ok {
+		fmt.Fprintf(os.Stderr, "FAIL\n")
+		os.Exit(2)
+	}
+}
+
+func count(line uint32) uint32 {
+	// Linear search is fine.
+	for i := range coverTest.Count {
+		lo, hi := coverTest.Pos[3*i], coverTest.Pos[3*i+1]
+		if lo <= line && line <= hi {
+			return coverTest.Count[i]
+		}
+	}
+	return 0
+}

cmd/cover/testdata/test.go

@@ -0,0 +1,105 @@
+// Copyright 2013 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.
+
+// This program is processed by the cover command, and then testAll is called.
+// The test driver in main.go can then compare the coverage statistics with expectation.
+
+// The word LINE is replaced by the line number in this file. When the file is executed,
+// the coverage processing has changed the line numbers, so we can't use runtime.Caller.
+
+package main
+
+const anything = 1e9 // Just some unlikely value that means "we got here, don't care how often"
+
+func testAll() {
+	testSimple()
+	testBlockRun()
+	testFor()
+	testSwitch()
+	testSelect1()
+	testSelect2()
+}
+
+func testSimple() {
+	check(LINE, 1)
+}
+
+func testFor() {
+	for i := 0; i < 10; i++ {
+		check(LINE, 10)
+	}
+}
+
+func testBlockRun() {
+	check(LINE, 1)
+	{
+		check(LINE, 1)
+	}
+	{
+		check(LINE, 1)
+	}
+	check(LINE, 1)
+	{
+		check(LINE, 1)
+	}
+	{
+		check(LINE, 1)
+	}
+	check(LINE, 1)
+}
+
+func testSwitch() {
+	for i := 0; i < 5; i++ {
+		switch i {
+		case 0:
+			check(LINE, 1)
+		case 1:
+			check(LINE, 1)
+		case 2:
+			check(LINE, 1)
+		default:
+			check(LINE, 2)
+		}
+	}
+}
+
+func testSelect1() {
+	c := make(chan int)
+	go func() {
+		for i := 0; i < 1000; i++ {
+			c <- i
+		}
+	}()
+	for {
+		select {
+		case <-c:
+			check(LINE, anything)
+		case <-c:
+			check(LINE, anything)
+		default:
+			check(LINE, 1)
+			return
+		}
+	}
+}
+
+func testSelect2() {
+	c1 := make(chan int, 1000)
+	c2 := make(chan int, 1000)
+	for i := 0; i < 1000; i++ {
+		c1 <- i
+		c2 <- i
+	}
+	for {
+		select {
+		case <-c1:
+			check(LINE, 1000)
+		case <-c2:
+			check(LINE, 1000)
+		default:
+			check(LINE, 1)
+			return
+		}
+	}
+}