Repository Test - Go Data Layer Testing Skill

Name: repository-test
Rating: 87
Author: nikolayk812

This skill provides guidance on testing repository implementations using real databases with comprehensive error coverage.

Core Principles

•Real Database Testing: Use testcontainers with PostgreSQL, not mocks
•Domain Model Focus: Test with domain models only, never SQLC types
•One Assert Per Domain Model: Create assert[ModelName] for EVERY domain model returned by repository methods (e.g., assertCart, assertOrder)
•Mandatory Custom Assertions: Compare all fields except generated ones (ID, timestamps). NEVER use assert.Equal on individual model fields
•Comprehensive Error Coverage: Test validation, not found, and state-dependent errors using arrangeState patterns
•Table-Driven Structure: Organize with clear test scenarios and expected outcomes
•Consistent Cleanup: Use defer suite.deleteAll() once per test method, never per test case

Key Patterns

Suite Structure

type repositorySuite struct {
    suite.Suite
    repo port.Repository
    pool *pgxpool.Pool
}

Table-Driven Tests

tests := []struct {
    name         string
    buildModel   func() domain.Model
    arrangeState func(uuid.UUID) error  // arrange state for test case before the operation
    useModelID   func() uuid.UUID       // override which model ID to use, if nil use the inserted one
    wantError    string
}{
    // Must test ALL error categories:
    {name: "valid input: ok", buildModel: randomModel},
    {name: "empty id: error", useModelID: func() uuid.UUID { return uuid.Nil }, wantError: "id is empty"},
    {name: "non-existing: not found", useModelID: randomUUID, wantError: "q.Method: record not found"},
    {name: "soft-deleted: not found", arrangeState: softDelete, wantError: "q.Method: record not found"},
}

Forbidden Patterns

// NEVER do manual field assertions
require.Equal(t, expected.OwnerID, actual.OwnerID)  // ❌ FORBIDDEN
require.Len(t, actual.Items, len(expected.Items))   // ❌ FORBIDDEN

// ALWAYS use comprehensive model assertions
assertCart(t, expected, actual)                     // ✅ REQUIRED

Custom Assertions (Required for Each Model)

// MUST create for every domain model - compare ALL fields except generated ones
func assertModel(t *testing.T, expected, actual domain.Model) {
    opts := cmp.Options{
        cmpopts.IgnoreFields(domain.Model{}, "CreatedAt", "UpdatedAt", "ID"),
        customComparers,
    }
    assert.Empty(t, cmp.Diff(expected, actual, opts))
    assert.False(t, actual.CreatedAt.IsZero())
}

Testing Guidelines

•Package: Use repository_test package for interface testing
•Data Generation: Use gofakeit for realistic random data via helper functions
•Container Setup: Initialize with migration scripts via postgres.WithInitScripts()
•Test Names: Follow "action + condition: expected result" pattern
•Error Messages: Verify exact error messages match repository implementations
•Cleanup Pattern: One defer suite.deleteAll() per test method only