Writing Multiple Test Cases Together

In this lesson you will learn how to run several test cases together in Go, and understand what a body of unit tests looks like. This is for anyone searching for "Go unit test how to write".

Testing one function against several input patterns at once is called unit testing. Preparing a spread of cases - normal values, boundary values, special values - helps you find bugs early.

The sample code collects several cases in a slice of testCase structs, feeds each one to add() in a for loop, checks the result, and counts the successes in passed. Boundary-value testing - deliberately checking special situations such as zero, maximum values, and empty data - is an important perspective.

A common stumbling block for beginners is testing only the happy path and forgetting boundary values such as zero or negative numbers. Covering the cases that are easy to overlook is what matters.

Real Go development uses the standard testing package with the go test command, but the underlying idea is exactly what you learn here.

📖 Reference code

package main

import "fmt"

func add(a, b int) int {
    return a + b
}

type testCase struct {
    a, b, expected int
}

func main() {
    testCases := []testCase{
        {2, 3, 5},
        {-1, 1, 0},
        {0, 0, 0},
    }

    passed := 0
    for i, tc := range testCases {
        result := add(tc.a, tc.b)
        ok := result == tc.expected
        if ok {
            passed++
        }
        status := "FAIL"
        if ok {
            status = "OK"
        }
        fmt.Printf("Test %d: %s\n", i+1, status)
    }
    fmt.Printf("%d/%d passed\n", passed, len(testCases))
}

✍️ Your code

Type your code, then press "Run"

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