Testing Strategies

Table-Driven Tests: The idiomatic Go testing pattern. Define inputs and expected outputs as a slice of structs, iterate and run each as a subtest.

func TestAuthorizePayment(t testing.T) {
    tests := []struct {
        name       string
        balance    string
        amount     string
        wantStatus string
        wantErr    bool
    }{
        {"sufficient balance", "500.00", "100.00", "authorized", false},
        {"exact balance", "100.00", "100.00", "authorized", false},
        {"insufficient balance", "50.00", "100.00", "", true},
        {"zero amount", "500.00", "0.00", "", true},
        {"negative amount", "500.00", "-10.00", "", true},
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t testing.T) {
            svc := NewPaymentService(mockRepo, mockChain)
            result, err := svc.Authorize(ctx, tt.balance, tt.amount)
            if (err != nil) != tt.wantErr {
                t.Fatalf("err = %v, wantErr = %v", err, tt.wantErr)
            }
            if !tt.wantErr && result.Status != tt.wantStatus {
                t.Errorf("status = %s, want %s", result.Status, tt.wantStatus)
            }
        })
    }
}

Mocks via Interfaces: Define behavior as interfaces, inject mock implementations in tests.

type BlockchainClient interface {
    SendTransaction(ctx context.Context, tx types.Transaction) error
    GetBalance(ctx context.Context, addr common.Address) (big.Int, error)
}

type mockBlockchainClient struct {
    sendErr    error
    balance    big.Int
    balanceErr error
}

func (m mockBlockchainClient) SendTransaction(ctx context.Context, tx types.Transaction) error {
    return m.sendErr
}

No mocking frameworks needed — Go interfaces make manual mocks trivial.

Integration Tests with testcontainers:

func TestSettlementIntegration(t testing.T) {
    if testing.Short() {
        t.Skip("skipping integration test")
    }
    // Spin up a real Postgres in Docker
    pgContainer, _ := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
        ContainerRequest: testcontainers.ContainerRequest{
            Image: "postgres:15",
            Env:   map[string]string{"POSTGRES_PASSWORD": "test"},
        },
        Started: true,
    })
    defer pgContainer.Terminate(ctx)
    // Run migrations, test against real DB
}

Use -short flag to skip integration tests in CI fast path. Full integration suite runs on merge.