Writing Tests

Test Syntax

Tests are declared with the test keyword followed by a description string and a block:

test "descriptive name for the test" {
    // test body
}

The description appears in test output, so make it meaningful:

✓ "user can log in with valid credentials"
✓ "empty list returns None for find"
✗ "test1" (not descriptive)

Serial Tests

By default, tests run concurrently for speed. Use @serial when a test needs isolation:

@serial test "modifies global state" {
    // This test runs alone, not concurrently with others
}

Use @serial when:

Tests modify shared state
Tests depend on specific timing
Tests use resources that can’t be shared

Testing Functions

Test regular functions by calling them and asserting on results:

fn factorial(n: Int) -> Int {
    if n <= 1 {
        return 1;
    }
    return n * factorial(n - 1);
}

test "factorial of 5 is 120" {
    assert_eq(factorial(5), 120);
}

test "factorial of 0 is 1" {
    assert_eq(factorial(0), 1);
}

test "factorial of 1 is 1" {
    assert_eq(factorial(1), 1);
}

Testing Agents

Test agents by spawning them with mocked LLM responses:

agent Summariser {
    topic: String

    on start {
        let summary = try divine("Summarise: {self.topic}");
        yield(summary);
    }

    on error(e) {
        yield("Error occurred");
    }
}

test "summariser returns LLM response" {
    mock divine -> "This is a summary of quantum physics.";

    let result = await summon Summariser { topic: "quantum physics" };
    assert_eq(result, "This is a summary of quantum physics.");
}

Test Body Semantics

Test bodies are async by default — you can use await and summon without special syntax:

test "two agents can run concurrently" {
    mock divine -> "Result A";
    mock divine -> "Result B";

    let a = summon Researcher { topic: "A" };
    let b = summon Researcher { topic: "B" };

    let result_a = await a;
    let result_b = await b;

    assert_eq(result_a, "Result A");
    assert_eq(result_b, "Result B");
}

Organising Tests

Keep tests close to the code they test:

src/
├── auth.sg
├── auth_test.sg      # Tests for auth.sg
├── payments.sg
└── payments_test.sg  # Tests for payments.sg

Or use a dedicated test directory:

src/
├── main.sg
└── lib/
    ├── utils.sg
    └── utils_test.sg

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