Introduction
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 0.005sSub 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：
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？
- 大部分的测试(自动化)应该是开发人员自己做。
- 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)
- 测试可以确保您始终可以运送主分支
- 测试确定软件行为（做什么、不做什么）
- 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'
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