Unit Tests

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Unit Tests in Go
by yhuang Go testing.T fmt fmt.Sprintf testing
Unit testing is an important part of writing principled Go programs. The testing package provides the tools we need to write unit tests and the go test command runs tests.
package main

import (
    "fmt"
    "testing"
)

// Run the test in your shell with:
// go test -v

func IntMin(a, b int) int {
    if a < b {
        return a
    } else {
        return b
    }
}

// A test is created by writing a function with a name beginning with Test.
func TestIntMinBasic(t *testing.T) {
    ans := IntMin(2, -2)
    if ans != -2 {

        // t.Error* will report test failures but continue executing the test.
        // t.Fail* will report test failures and stop the test immediately.
        t.Errorf("IntMin(2, -2) = %d; want -2", ans)
    }
}

// Writing tests can be repetitive, so it’s idiomatic to use a table-driven style,
// where test inputs and expected outputs are listed in a table and a single loop
// walks over them and performs the test logic.
func TestIntMinTableDriven(t *testing.T) {
    var tests = []struct {
        a, b int
        want int
    }{
        {0, 1, 0},
        {1, 0, 0},
        {2, -2, -2},
        {0, -1, -1},
        {-1, 0, -1},
    }

    // t.Run enables running “subtests”, one for each table entry.
    // These are shown separately when executing go test -v.
    for _, tt := range tests {

        testname := fmt.Sprintf("%d,%d", tt.a, tt.b)
        t.Run(testname, func(t *testing.T) {
            ans := IntMin(tt.a, tt.b)
            if ans != tt.want {
                t.Errorf("got %d, want %d", ans, tt.want)
            }
        })
    }
}