Go 语言 Example 函数：文档示例而非差异化测试工具

package mypackage

import (
    "fmt"
    "strings"
)

// Greeter struct represents a greeting mechanism.
type Greeter struct {
    Name string
}

// Greet returns a greeting message.
func (g Greeter) Greet() string {
    return fmt.Sprintf("Hello, %s!", g.Name)
}

// ExampleGreeter_Greet 示例展示了 Greeter.Greet 方法的使用。
func ExampleGreeter_Greet() {
    g := Greeter{Name: "Gopher"}
    fmt.Println(g.Greet())
    // Output:
    // Hello, Gopher!
}

// ExampleSplitString 示例展示了如何使用 strings.Split 函数。
func ExampleSplitString() {
    s := "apple,banana,cherry"
    parts := strings.Split(s, ",")
    for _, part := range parts {
        fmt.Println(part)
    }
    // Output:
    // apple
    // banana
    // cherry
}

package mypackage

import (
    "bytes"
    "fmt"
    "io/ioutil"
    "strings"
    "testing"

    "github.com/pmezard/go-difflib/difflib" // 一个常用的 Go 语言 diff 库
)

// ProcessText 模拟一个文本处理函数，可能产生较长的输出。
func ProcessText(input string) string {
    lines := strings.Split(input, "\n")
    var result []string
    for i, line := range lines {
        result = append(result, fmt.Sprintf("%d: %s (processed)", i+1, strings.ToUpper(line)))
    }
    return strings.Join(result, "\n")
}

// TestProcessTextWithDiff 演示如何在 Test 函数中进行差异化比较。
func TestProcessTextWithDiff(t *testing.T) {
    input := `hello world
go programming
testing in go`

    // 预期输出，通常会从一个单独的黄金文件（golden file）加载，或直接定义
    expectedOutput := `1: HELLO WORLD (processed)
2: GO PROGRAMMING (processed)
3: TESTING IN GO (processed)`

    actualOutput := ProcessText(input)

    if actualOutput != expectedOutput {
        t.Errorf("Processed text mismatch.\nGot:\n%s\nWant:\n%s", actualOutput, expectedOutput)

        // 使用 difflib 生成并打印差异
        diff := difflib.UnifiedDiff{
            A:        difflib.SplitLines(expectedOutput),
            B:        difflib.SplitLines(actualOutput),
            FromFile: "Expected",
            ToFile:   "Actual",
            Context:  3, // 显示上下文行数
        }
        text, err := difflib.Get  DiffString(diff)
        if err != nil {
            t.Fatalf("Failed to generate diff: %v", err)
        }
        t.Logf("--- Diff ---\n%s", text)
    }
}

// TestProcessTextWithGoldenFile 演示使用黄金文件进行测试。
func TestProcessTextWithGoldenFile(t *testing.T) {
    input := `first line
second line
third line`

    actualOutput := ProcessText(input)

    // 预期输出存储在外部文件中 (e.g., testdata/golden.txt)
    goldenFile := "testdata/golden.txt"
    expectedBytes, err := ioutil.ReadFile(goldenFile)
    if err != nil {
        t.Fatalf("Failed to read golden file %s: %v", goldenFile, err)
    }
    expectedOutput := string(expectedBytes)

    if actualOutput != expectedOutput {
        t.Errorf("Processed text mismatch with golden file %s.", goldenFile)
        // 如果是第一次运行或需要更新黄金文件，可以写入
        // ioutil.WriteFile(goldenFile, []byte(actualOutput), 0644)
        // t.Logf("Golden file updated. Please review changes.")

        diff := difflib.UnifiedDiff{
            A:        difflib.SplitLines(expectedOutput),
            B:        difflib.SplitLines(actualOutput),
            FromFile: goldenFile,
            ToFile:   "Actual Output",
            Context:  3,
        }
        text, err := difflib.Get  DiffString(diff)
        if err != nil {
            t.Fatalf("Failed to generate diff: %v", err)
        }
        t.Logf("--- Diff ---\n%s", text)
    }
}

// testdata/golden.txt 内容示例:
// 1: FIRST LINE (PROCESSED)
// 2: SECOND LINE (PROCESSED)
// 3: THIRD LINE (PROCESSED)