write-tests

name: write-tests description: Write spec-aligned Dada tests. Use when creating new test files, organizing tests to match the specification, or adding test coverage for language features.

Writing Spec-Aligned Dada Tests

Directory Structure

Tests mirror the spec directory structure under tests/:

spec/src/syntax/string-literals.md     →  tests/syntax/string_literals/
spec/src/syntax/literals.md            →  tests/syntax/literals/

Within each test directory, organize by spec section:

tests/syntax/string_literals/
├── delimiters/
│   └── quoted.dada                    # #:spec syntax.string-literals.delimiters.quoted
├── type.dada                          # #:spec syntax.string-literals.type
├── escape_sequences/
│   ├── backslash.dada                 # #:spec syntax.string-literals.escape-sequences.backslash
│   ├── invalid.dada                   # #:spec syntax.string-literals.escape-sequences.invalid
│   └── ...
└── interpolation/
    └── brace_escaping.dada            # #:spec syntax.string-literals.interpolation.brace-escaping

Ad-hoc tests that don't correspond to a spec paragraph go in tests/adhoc/.

Spec Paragraph ID Resolution

IDs are built from the spec file path and headings:

1. File prefix: spec/src/syntax/string-literals.md → syntax.string-literals
   • README.md is special: only the parent directory becomes the prefix
2. Heading segments: H2+ headings, lowercased, spaces/underscores → hyphens
   • H1 is skipped (it's the page title, already in the file prefix)
3. Block local name: From :::{spec} local_name directive
   • If the first token looks like a tag (rfc0001, unimpl), there's no local name
4. Inline sub-paragraph: From {spec}`name` inside a block

Examples

# String Literals                         ← H1: skipped (in file prefix)
## Escape Sequences                       ← H2: "escape-sequences"
:::{spec} rfc0001                         ← Block: no local name (rfc0001 is a tag)
* {spec}`backslash` `\\` produces...      ← Inline: "backslash"
:::
:::{spec} invalid rfc0001                 ← Block: local name = "invalid"
:::

Resulting IDs:

• syntax.string-literals.escape-sequences (the block)
• syntax.string-literals.escape-sequences.backslash (inline)
• syntax.string-literals.escape-sequences.invalid (named block)

Writing Test Files

Basic test structure

#:spec syntax.string-literals.delimiters.quoted
#:skip_codegen

async fn main() {
    print("hello").await
    print("").await
}

Error test (diagnostic expectations)

#:spec syntax.string-literals.escape-sequences.invalid
#:skip_codegen

async fn main() {
    print("\a").await
    #!      ^ /invalid escape
}

The ^ must be at the exact column of the error span on the previous line. Use /pattern (NO closing /) for regex matching.

Type probe test

#:spec syntax.string-literals.type
#:skip_codegen

fn main() {
    let x = "hello"
    #?  ^ VariableType: String
}

VariableType shows the declared type without permissions. Use ExprType for expression types. Multiple ^^ carets match multi-byte spans.

Known Issues

Brace escaping in strings

The tokenizer's delimited() function doesn't skip over string literal contents when scanning for matching braces. Unbalanced { or } inside strings will confuse brace-depth tracking. Workaround: Use balanced \{...\} pairs in test strings:

# Good — balanced braces
print("\{\}").await
print("hello\{world\}").await

# Bad — unbalanced brace causes parse errors
print("\{").await

This will be fixed when string interpolation is implemented.

Checklist for New Tests

1. Identify the spec paragraph ID for the feature being tested
2. Create the test file in the matching directory structure
3. Add #:spec <paragraph-id> annotation
4. Add #:skip_codegen if the test doesn't need WebAssembly generation
5. Write test code exercising the feature
6. Add #! annotations for expected errors or #? probes for type checking
7. Run with cargo dada test --porcelain <test-file> to verify
8. Check .test-report.md if the test fails