Unit Tests

The package test contains a library for unit tests, and a language extension for Basic Storm that allows easy creation of tests and test suites. According to the library, tests are individual assert statements, that are in turn organized into suites. The suites are simply functions that accept zero parameters and return a test.TestResult. Tests can be further organized into packages.

As mentioned in the language reference, it is possible to run test suites using the -t or -T parameter on the command line.


The library provides a number of types and functions that support the creation and execution of test suites. In particular, the type test.TestResult represents the result of executing one or more test suites. It has the following members:

As with other types, test.TestResult can be printed. This produces a summary of the test results.

The library also contains a number of functions to execute test suites:

Language Extension

As mentioned above, the package also contains a language extension for Basic Storm. It introduces the keyword suite for defining a test suite. Inside a test suite, the test keyword becomes available to test some behavior, and the abort statement to abort testing.

Defining a test suite looks as follows:

use test;

// Create a test suite. Generates a function.
suite MySuite {
    // Check for equality.
    test f(1) == 3;
    // Check for inequality.
    test f(2) < 8;
    // Test boolean expressions.
    test true;
    // Test that a particular exception is thrown.
    test f(3) throws InternalError;

// Function to test, can be located elsewhere.
Nat f(Nat x) {
    if (x >= 3)
        throw InternalError("Error");
    return x + 1; // change to 2 to make tests pass

As can be seen above, the test keyword recognizes the standard comparison operators in Basic Storm (i.e. ==, !=, >, <, >=, <=, is, !is). Operators added via extensions might not be visible. Adding operators for the test syntax requires extending the test.STestOp production. When any of them fails, it will print a diagnostic message of the following form:

Failed: fn(1) == 3 ==> 2 != 3

As can be seen, the left-hand side of the arrow ==> prints the original expression, and the right hand side prints the actual values of the expression, along with the inverse of the operator to illustrate the issue.