Creating a Test Automation Harness for Jest with Typescript

Scenario

We have a simple function contains that tests whether a string contains another:

/**
 * Test whether the target string contains the contained string.
 *
 * @param target The string that should contains the element
 * @param contained The possibly contained string
 * @return true if the `target` string contains the `contained` string, false otherwise
 * @example
 * ```
 * expect(contains('foobar', 'foo')).toBeTruthy()
 * ```
 */
export function contains(target: string, contained: string):boolean {
   return target.indexOf(contained) >= 0;
}

And we want to test it by passing by passing in valid and invalid data to a test function like this:

test('contains', ()=>{
   runtest(testdata, contains)
})

Approach

Harness

We will place our test data in a harness like this:

const testdata: TestData[] = [
{
it: 'should test contains',
args: ['foo'],
valid: ['foo', 'foobar', 'bazfoo'],
invalid: ['bar', 'fobar'],
}]

Note that the args contains the second argument we are passing to contains .

If multiple arguments are being tested we can pass them in via each . For example:

each: ['baz', 'bar', 'beech']

The TestData interface

export interface TestData {
it: string
args?: any
each?: any[]
valid: any[],
invalid: any[]
}

Test Utility Function

More Examples

See the Firefly Semantics ValidatorTS Tests:

GitHub - fireflysemantics/validatorts: Typescript conversion of ValidatorJS