Snippet

Writing Parallel Table-Driven Tests in Go

Table-driven tests in Go isolate test inputs and expected outputs in a clean structure. Adding t.Parallel() inside the dynamically running t.Run subtests allows Go's test runner to execute them concurrently, optimizing execution speed.

snippet.go

package main
 
import "testing"
 
func CalculateDiscount(price int) int {
	if price > 100 {
		return price - 20
	}
	return price
}
 
func TestCalculateDiscount(t *testing.T) {
	tests := []struct {
		name     string
		input    int
		expected int
	}{
		{"No discount for low price", 50, 50},
		{"Apply discount for high price", 150, 130},
	}
 
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()
			got := CalculateDiscount(tc.input)
			if got != tc.expected {
				t.Errorf("got %d, want %d", got, tc.expected)
			}
		})
	}
}

Breakdown

tests := []struct {

Defines a slice of anonymous structs representing the test cases.

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

Executes a subtest for each test case dynamically naming it.

t.Parallel()

Signals that this subtest can run concurrently with other parallel tests.

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Writing Parallel Table-Driven Tests in Go

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