testing — Claude Code skill: write and run tests

---
name: testing
description: How to write tests, when to use each type of test, and how to run them. Contains information about conversion of `.test` to `.sqltest`, and how to write `.sqltest` and rust tests
---
# Testing Guide

## Test Types & When to Use

| Type | Location | Use Case |
|------|----------|----------|
| `.sqltest` | `sqlite/conformance/sqlite-sqltests/` | SQL compatibility. **Preferred for new tests** |
| TCL `.test` | `testing/` | Legacy SQL compat (being phased out) |
| Rust integration | `tests/integration/` | Regression tests, complex scenarios |
| Fuzz | `tests/fuzz/` | Complex features, edge case discovery |

**Note:** TCL tests are being phased out in favor of the `.sqltest` suites in `sqlite/conformance/`. The `.sqltest` format allows the same test cases to run against multiple backends (CLI, Rust bindings, etc.).

## Running Tests

```bash
# Main test suite (TCL compat, sqlite3 compat, Python wrappers)
make test

# Single TCL test
make test-single TEST=select.test

# SQL test runner
make -C sqlite/conformance run-cli

# OR
cargo run -p sqltest -- run <test-file or directory>

# Rust unit/integration tests (full workspace)
cargo test
```

## Writing Tests

### .sqltest (Preferred)
```
@database :default:

test example-addition {
    SELECT 1 + 1;
}
expect {
    2
}

test example-multiple-rows {
    SELECT id, name FROM users WHERE id < 3;
}
expect {
    1|alice
    2|bob
}
```
Location: `sqlite/conformance/sqlite-sqltests/*.sqltest`

You must start converting TCL tests with the `convert` command from the test runner (e.g `cargo run -- convert <TCL_test_path> -o <out_dir>`). It is not always accurate, but it will convert most of the tests. If some conversion emits a warning you will have to write by hand whatever is missing from it (e.g unroll a for each loop by hand). Then you need to verify the tests work by running them with `make -C sqlite/conformance run-rust`, and adjust their output if something was wrong with the conversion. Also, we use harcoded databases in TCL, but with `.sqltest` we generate the database with a different seed, so you will probably need to change the expected test result to match the new database query output. Avoid changing the SQL statements from the test, just change the expected result 

### TCL
```tcl
do_execsql_test_on_specific_db {:memory:} test-name {
  SELECT 1 + 1;
} {2}
```
Location: `testing/*.test`

### Rust Integration
```rust
// tests/integration/test_foo.rs
#[test]
fn test_something() {
    let conn = Connection::open_in_memory().unwrap();
    // ...
}
```

### Assertions

Prefer the [`asserting`](https://github.com/innoave/asserting) crate for anything more than trivial assertions. The assertions it offers are extensive
and make tests more readable. Some simple examples:

```rust
use asserting::prelude::*;

assert_that!(conn.execute("SELECT * FROM t1;")).is_err();
assert_that_code!(|| parse(bad_input)).panics_with_message("unexpected token");

assert_that!(&rows)
    .has_length(3)
    .any_satisfies(|r| r
    .name == "bob")
    .first_element_ref()
    .is_equal_to(&Row { id: 1, name: "alice".into() });

assert_that!(&header)
    .named("page 2 header")
    .satisfies_with_message("be a leaf table page", |h| h[0] == 0x0d);

// soft assertions: mark the test as failed but don't stop
verify_that!(&plan)
    .starts_with("SEARCH")
    .contains("USING INDEX")
    .soft_panic();
```

`crate::assertions` adds `row!` for result rows, plus `column` and query-plan
assertions:

```rust
use crate::assertions::{AssertColumn, AssertQueryPlan, Cell, NULL};

assert_that!(limbo_exec_rows(&conn, "SELECT id, name FROM t ORDER BY id"))
    .is_equal_to(vec![row![1, "alice"], row![2, NULL]]);

assert_that!(limbo_exec_rows(&conn, "SELECT id FROM t WHERE id = 1"))
    .single_element()
    .is_equal_to(row![1]);

assert_that!(limbo_exec_rows(&conn, "SELECT id, name FROM t"))
    .column(1)
    .contains(Cell::from("alice"));

assert_that!(limbo_exec_rows(&conn, "EXPLAIN QUERY PLAN SELECT id FROM t WHERE name = 'a'"))
    .uses_index("idx_name")
    .searches_table("t")
    .has_table_access_order(["t"]);
```

## Key Rules

- Every functional change needs a test
- Test must fail without change, pass with it
- Prefer in-memory DBs: `:memory:` (sqltest) or `{:memory:}` (TCL)
- Don't invent new test formats. Follow existing patterns
- Write tests first when possible

## Test Database Schema

`testing/system/testing.db` has `users` and `products` tables. See [docs/testing.md](../../../docs/testing.md) for schema.

## Logging During Tests

```bash
RUST_LOG=none,turso_core=trace make test
```
Output: `testing/system/test.log`. Warning: very verbose.