Snippet

Writing Maintainable Table-Driven Unit Tests

Table-driven testing is an idiomatic pattern in Go. By defining a list of test cases in a slice of structs, you can easily add new test inputs and expected outputs without duplicating assertion logic, leading to cleaner and more maintainable tests.

snippet.go

package main
 
import (
	"testing"
)
 
func Add(a, b int) int {
	return a + b
}
 
func TestAdd(t *testing.T) {
	tests := []struct {
		name     string
		a, b     int
		expected int
	}{
		{"positive numbers", 2, 3, 5},
		{"negative numbers", -1, -1, -2},
		{"mixed numbers", -1, 5, 4},
	}
 
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			result := Add(tt.a, tt.b)
			if result != tt.expected {
				t.Errorf("Add(%d, %d) = %d; want %d", tt.a, tt.b, result, tt.expected)
			}
		})
	}
}

Breakdown

tests := []struct { ... }

Declares a slice of anonymous structs representing the test matrix, containing test names, inputs, and expected outcomes.

for _, tt := range tests

Iterates over each test case in the table, binding the current case to local scope variables.

t.Run(tt.name, func(t *testing.T) { ... })

Creates a subtest with its own reporting scope, making it easy to isolate and run specific test scenarios from the CLI.

t.Errorf(...)

Logs an assertion error if the output does not match expected value, but allows subsequent tests in the table to continue running.

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Writing Maintainable Table-Driven Unit Tests

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