Golang 测试

前言

关于 Go 测试，我们应该知道测试方式（或者说测试手段）、测试对象及测试原因。

How 测试方式

测试实现

举个例子。针对字符串分割函数（如下），实现单元测试。

package goTest import "strings" // Split slices s into all substrings separated by sep and // returns a slice of the substrings between those separators. func Split(s, sep string) []string { var result []string i := strings.Index(s, sep) for i > -1 { result = append(result, s[:i]) s = s[i+len(sep):] i = strings.Index(s, sep) } return append(result, s) } 

在当前目录下且一样的包名 goTest ，写一个简单的 go 测试函数，如下：

package goTest import ( "reflect" "testing" ) func TestSplit(t *testing.T) { got := Split("a/b/c", "/") want := []string{"a", "b", "c"} if !reflect.DeepEqual(want, got) { t.Fatalf("expected: %v, got: %v", want, got) } } 

测试函数必须以 Test 开头， 且必须携带一个 *testing.T 参数。 t *testing.T 提供改测试函数的打印、跳过、失败功能。

测试执行

当前目录下，执行 go test ，输出如下：

> go test PASS ok goTest 0.005s 

如果项目中存在多个 package ，若要执行所有包的测试可以在项目根目录下使用 go test ./... ，输出如下（例子：github.com/mattn/go-sqlite3）：

> go test ./... ok github.com/mattn/go-sqlite3 14.693s ? github.com/mattn/go-sqlite3/upgrade [no test files] 

代码测试覆盖率

还是以字符串分割函数为例， 获取当前代码测试覆盖率方式如下：

> go test -coverprofile=c.out PASS coverage: 100.0% of statements ok goTest 0.005s 

数据显示覆盖率为 100% 。若要以 HTML 方式显示可以使用命令 go tool cover -html=c.out 。

【tip】 一行命令 cover 获取当前目录下的代码测试覆盖度。 在 ~/.bashrc 中添加如下命令：

cover () { local t=$(mktemp -t cover) go test $COVERFLAGS -coverprofile=$t $@ \ && go tool cover -func=$t \ && unlink $t } 

执行后获取的测试覆盖度结果如下：

> cover PASS coverage: 100.0% of statements ok goTest 0.008s goTest/wwg_split.go:7: Split 100.0% total: (statements) 100.0% 

问题：测试覆盖率 100% ，结束了？

多个测试用例的情况下，使用表组测试用例装填。更改 TestSplit 如下：

func TestSplit(t *testing.T) { tests := []struct{ input string sep string want []string }{ {input: "a/b/c", sep: "/", want: []string{"a", "b", "c"}}, {input: "a/b/c", sep: ",", want: []string{"a/b/c"}}, {input: "a/b/c/", sep: "/", want: []string{"a", "b", "c"}}, // trailing sep {input: "abc", sep: "/", want: []string{"abc"}}, } for _, tc := range tests { got := Split(tc.input, tc.sep) if !reflect.DeepEqual(tc.want, got) { t.Fatalf("expected: %v, got: %v", tc.want, got) } } } 

增加测试用例 trailing sep 后，执行测试，结果如下：

> go test --- FAIL: TestSplit (0.00s) wwg_split_test.go:23: expected: [a b c], got: [a b c ] FAIL exit status 1 FAIL goTest 0.005s 

根据该结果很难一下子在表组测试用例中查出是哪条。可以将 表组测试用例实现改为 map 形式 ，具体如下：

func TestSplit(t *testing.T) { tests := map[string]struct{ input string sep string want []string }{ "simple": {input: "a/b/c", sep: "/", want: []string{"a", "b", "c"}}, "wrong sep": {input: "a/b/c", sep: ",", want: []string{"a/b/c"}}, "trailing sep": {input: "a/b/c/", sep: "/", want: []string{"a", "b", "c"}}, "no sep": {input: "abc", sep: "/", want: []string{"abc"}}, } for name, tc := range tests { got := Split(tc.input, tc.sep) if !reflect.DeepEqual(tc.want, got) { t.Errorf("%s expected: %v, got: %v", name, tc.want, got) } } } 

执行测试结果如下：

> go test --- FAIL: TestSplit (0.00s) wwg_split_test.go:23: trailing sep expected: [a b c], got: [a b c ] FAIL exit status 1 FAIL goTest 0.005s 

Sub tests 使用，及 '%#v' format 使用，更改 TestSplit 如下：

func TestSplit(t *testing.T) { tests := map[string]struct{ input string sep string want []string }{ "simple": {input: "a/b/c", sep: "/", want: []string{"a", "b", "c"}}, "wrong sep": {input: "a/b/c", sep: ",", want: []string{"a/b/c"}}, "trailing sep": {input: "a/b/c/", sep: "/", want: []string{"a", "b", "c"}}, "no sep": {input: "abc", sep: "/", want: []string{"abc"}}, } for name, tc := range tests { t.Run(name, func(t *testing.T) { got := Split(tc.input, tc.sep) if !reflect.DeepEqual(tc.want, got) { t.Fatalf("%s expected: %#v, got: %#v", name, tc.want, got) } }) } } 

测试结果如下：

> go test --- FAIL: TestSplit (0.00s) --- FAIL: TestSplit/trailing_sep (0.00s) wwg_split_test.go:24: trailing sep expected: []string{"a", "b", "c"}, got: []string{"a", "b", "c", ""} FAIL exit status 1 FAIL goTest 0.005s 

更好的打印格式，可以访问：

• https://github.com/k0kubun/pp
• https://github.com/davecgh/go-spew
• https://github.com/google/go-cmp

使用 google/go-cmp 优化打印， 更改 TestSplit 如下：

 for name, tc := range tests { t.Run(name, func(t *testing.T) { got := Split(tc.input, tc.sep) diff := cmp.Diff(tc.want, got) if diff != "" { t.Fatalf(diff) } }) } 

执行测试结果如下：

> go test --- FAIL: TestSplit (0.00s) --- FAIL: TestSplit/trailing_sep (0.00s) wwg_split_test.go:29: []string{ "a", "b", "c", + "", } FAIL exit status 1 FAIL goTest 0.005s 

修复bug后 Split 代码如下：

// Split slices s into all substrings separated by sep and // returns a slice of the substrings between those separators. func Split(s, sep string) []string { var result []string i := strings.Index(s, sep) for i > -1 { result = append(result, s[:i]) s = s[i+len(sep):] i = strings.Index(s, sep) } if len(s) > 0 { result = append(result, s) } return result** } 

执行测试，结果如下：

> go test PASS ok goTest 0.006s > cover PASS coverage: 100.0% of statements ok goTest 0.006s goTest/wwg_split.go:7: Split 100.0% total: (statements) 100.0% 

What 测试对象

Q_1：Go 应该测试所有因子吗？

A_1：显然不是。

Q_2：何时编写测试? 1.编码完成后？ 2.编码前？ 3.其他人遍写测试，像QA、TE？ 4.项目设计人员编写测试？

A_2：编码的同时编写测试代码（TDD）Article TheThreeRulesOfTdd

Q_3：C 单元测试对象是 function ，Java 单元测试对象是 Class ，类内部的方法， Go 的单元测试对象是？

A_3：package 。测试行为，而非实施。 "The public API of a package declare this is what(行为) I do, not this is how(实施) I do it."

Why 测试原因

即使你不做代码测试，别人也会做。自己发现 issues 总比别人发现来得好，不是吗？

1. 大部分的测试(自动化)应该是开发人员自己做。
2. 手工测试不应该是你测试的主体部分，因为手工测试的复杂度为O(n)
3. 测试可以确保您始终可以运送主分支
4. 测试确定软件行为（做什么、不做什么）
5. 测试让你有信心修改他人的代码

总结

• You should write tests.
• You should write tests at the same time as you write your code.
  Each Go package is a self contained unit.
• Your tests should assert the observable behaviour of your package, not its implementation.
• You should design your packages around their behaviour, not their implementation.

【注】部分资料源于GopherChina 2019 - 'How to write testable code'
本文链接：GO TESTING;HOW,WHAT,WHY

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