testing.go

//
// gobyexample.com
// Testing
// testing.go
//
package main

import (
    "fmt"
    "testing"
)

// We’ll be testing this simple implementation of an 
// integer minimum. Typically, the code we’re testing
// would be in a source file named something like intutils.go,
// and the test file for it would then be named intutils_test.go.
func IntMin(a, b int) int {
    if a < b {
        return a
    }
    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.Fatal* 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)
            }
        })
    }
}