---

name: testing-strategies description: Testing patterns including unit, integration, E2E tests and language-specific frameworks. agents: [tess] triggers: [test, coverage, unit test, integration test, e2e]

Testing Strategies

Comprehensive testing patterns for ensuring code quality through automated tests.

Testing Approach

1. Unit Tests - Test individual functions/methods
2. Integration Tests - Test component interactions
3. E2E Tests - Test full user flows
4. Edge Cases - Cover boundary conditions
5. Error Handling - Test failure scenarios

Testing Guidelines

• Write tests that document behavior
• Use descriptive test names
• Follow AAA pattern (Arrange, Act, Assert)
• Mock external dependencies appropriately
• Keep tests fast and deterministic
• Test edge cases and error paths
• Aim for 80%+ coverage

Language-Specific Testing

Rust

Copycargo test --workspace
cargo test --workspace -- --nocapture  # Show output
cargo tarpaulin --out Html  # Coverage

Unit Test Pattern:

Copy#[cfg(test)]
mod tests {
    use super::*;
    use proptest::prelude::*;

    #[test]
    fn test_user_creation() {
        let user = User::new("test@example.com", "password123");
        assert!(user.is_ok());
    }

    // Property-based testing
    proptest! {
        #[test]
        fn test_email_validation(email in "[a-z]+@[a-z]+\\.[a-z]+") {
            let result = validate_email(&email);
            prop_assert!(result.is_ok());
        }
    }
}

Integration Test Pattern:

Copy// tests/integration_test.rs
use sqlx::PgPool;

#[sqlx::test]
async fn test_user_repository(pool: PgPool) {
    let repo = UserRepository::new(pool);
    let user = repo.create("test@example.com").await.unwrap();
    assert_eq!(user.email, "test@example.com");
}

Async Testing:

Copy#[tokio::test]
async fn test_async_operation() {
    let result = async_function().await;
    assert!(result.is_ok());
}

TypeScript

Copy# Bun projects
bun test
bun test --coverage

# Next.js projects
pnpm test
pnpm test --coverage
pnpm test:e2e  # Playwright

Effect Service Testing:

Copyimport { Effect, Layer } from "effect"
import { describe, it, expect } from "bun:test"

describe("UserService", () => {
  const TestDatabaseLayer = Layer.succeed(DatabaseService, {
    query: () => Effect.succeed([{ id: "1", name: "Test" }]),
  })

  it("should fetch users", async () => {
    const program = Effect.gen(function* () {
      const db = yield* DatabaseService
      return yield* db.query("SELECT * FROM users")
    })

    const result = await Effect.runPromise(
      program.pipe(Effect.provide(TestDatabaseLayer))
    )

    expect(result).toHaveLength(1)
  })
})

Schema Validation Testing:

Copyimport { Schema, Either } from "effect"

describe("UserSchema", () => {
  const UserSchema = Schema.Struct({
    email: Schema.String.pipe(Schema.pattern(/^[^@]+@[^@]+\.[^@]+$/)),
  })

  it("should validate correct data", () => {
    const result = Schema.decodeUnknownEither(UserSchema)({
      email: "test@example.com",
    })
    expect(Either.isRight(result)).toBe(true)
  })

  it("should reject invalid email", () => {
    const result = Schema.decodeUnknownEither(UserSchema)({
      email: "invalid",
    })
    expect(Either.isLeft(result)).toBe(true)
  })
})

React Component Testing:

Copyimport { render, screen, waitFor } from "@testing-library/react"

describe("UserList", () => {
  it("should display users", async () => {
    render(<UserList />)
    await waitFor(() => {
      expect(screen.getByText("Test User")).toBeInTheDocument()
    })
  })
})

Go

Copygo test ./... -v
go test ./... -cover
go test -race ./...  # Race detector
go test -bench=. ./...  # Benchmarks

Unit Test Pattern:

Copyfunc TestUserCreation(t *testing.T) {
    user, err := NewUser("test@example.com", "password")
    if err != nil {
        t.Fatalf("expected no error, got %v", err)
    }
    if user.Email != "test@example.com" {
        t.Errorf("expected email %q, got %q", "test@example.com", user.Email)
    }
}

Table-Driven Tests:

Copyfunc TestValidateEmail(t *testing.T) {
    tests := []struct {
        name  string
        email string
        valid bool
    }{
        {"valid email", "test@example.com", true},
        {"missing @", "testexample.com", false},
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            err := validateEmail(tt.email)
            if (err == nil) != tt.valid {
                t.Errorf("validateEmail(%q) = %v, want valid=%v", tt.email, err, tt.valid)
            }
        })
    }
}

Integration Test with testify:

Copyimport "github.com/stretchr/testify/assert"

func TestUserRepository(t *testing.T) {
    repo := NewUserRepository(testDB)
    user, err := repo.Create(context.Background(), "test@example.com")
    
    assert.NoError(t, err)
    assert.Equal(t, "test@example.com", user.Email)
}

Definition of Done

Before completing:

• All existing tests pass
• New tests cover the implementation
• Edge cases and error paths tested
• Effect services tested with mock Layers
• Schema validation tested with valid/invalid data
• Coverage meets project threshold (80%+)
• Tests are deterministic (no flakiness)