7.1.27. Testing with dastest

This tutorial covers the daslang testing framework: writing tests with [test], assertion functions, sub-tests, and running tests.

7.1.27.1. Setup

Import the testing framework:

require dastest/testing_boost public

7.1.27.2. Writing tests

Annotate functions with [test]. Each test receives a T? context:

[test]
def test_arithmetic(t : T?) {
    t |> equal(2 + 2, 4)
    t |> equal(3 * 3, 9, "multiplication")
}

7.1.27.3. Assertions

Function	Behavior
`t \|> equal(a, b)`	Check `a == b`; non-fatal on failure
`t \|> strictEqual(a, b)`	Check `a == b`; fatal on failure (stops test)
`t \|> success(cond)`	Check condition is truthy; non-fatal
`t \|> failure("msg")`	Always fails; non-fatal
`t \|> accept(value)`	Suppress unused warnings (no assertion)

All assertion functions accept an optional message string as the last argument.

7.1.27.4. Sub-tests

Group related checks with run:

[test]
def test_strings(t : T?) {
    t |> run("concat") @@(t : T?) {
        t |> equal("ab" + "cd", "abcd")
    }
    t |> run("length") @@(t : T?) {
        t |> equal(length("hello"), 5)
    }
}

Use @@(t : T?) { ... } (local function) for the callback.

7.1.27.5. Running tests

From the command line:

daslang.exe dastest/dastest.das -- --test path/to/test.das

To test an entire directory:

daslang.exe dastest/dastest.das -- --test path/to/tests/

7.1.27.6. Folder filtering with `.das_test`

When dastest scans a directory, it visits all subfolders by default. A .das_test file at the root of the test path lets you control which folders are visited.

If dastest finds a .das_test file in the --test directory, it compiles and simulates it, then calls its can_visit_folder function for every subfolder it encounters during scanning. The function receives the folder name and a bool pointer — set it to false to skip the folder. If the function returns without writing to the pointer, the folder is visited (default true).

Here is the .das_test used by the main tests/ directory:

options gen2
options indenting = 4

require daslib/rtti
require strings

[export, pinvoke]
def can_visit_folder(folder_name : string; var result : bool?) {
    if (folder_name == "dasHV" || folder_name == "dasPUGIXML") {
        *result = false
        return
    }
    if (folder_name == "jit_tests" || folder_name == ".jitted_scripts") {
        let args <- get_command_line_arguments()
        for (arg in args) {
            if (arg == "--use-aot") {
                *result = false
                return
            }
        }
    }
}

The function must be [export, pinvoke] because dastest calls it from a different context via invoke_in_context.

dasHV and dasPUGIXML are always skipped from the main test scan because their boost modules register global macros that can interfere with subsequent compilations. Run them separately with --test tests/dasHV or --test tests/dasPUGIXML.

has_module (from the rtti module) can be used in .das_test to check whether a module is linked into the current binary. For example, has_module("dashv") returns true only when dasHV is enabled.

The get_command_line_arguments() call reads the command-line arguments passed to the runner. This example uses it to skip JIT-only test folders when running in AOT mode (--use-aot).

Key points:

The .das_test file is a regular daslang script — it can require modules and use any logic.
The file is only loaded when dastest scans a directory. Running dastest on a single .das file bypasses .das_test entirely.
Files whose names start with _ are still skipped regardless of .das_test (this is a file-level convention, not a folder one).
If no .das_test file exists, all subfolders are visited.