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AVA comes bundled with a TypeScript definition file. This allows developers to leverage TypeScript for writing tests.
This guide assumes you've already set up TypeScript for your project. Note that AVA's definition has been tested with version 2.8.3.
You can configure AVA to recognize TypeScript files. Then, with ts-node
installed, you can compile them on the fly:
{
"ava": {
"compileEnhancements": false,
"extensions": [
"ts"
],
"require": [
"ts-node/register"
]
}
}
It's worth noting that with this configuration tests will fail if there are TypeScript build errors. If you want to test while ignoring these errors you can use ts-node/register/transpile-only
instead of ts-node/register
.
Add a test
script in the package.json
file. It will compile the project first and then run AVA.
{
"scripts": {
"test": "tsc && ava"
}
}
Make sure that AVA runs your built TypeScript files.
Create a test.ts
file.
import test from 'ava';
const fn = async () => Promise.resolve('foo');
test(async (t) => {
t.is(await fn(), 'foo');
});
Using macros
In order to be able to assign the title
property to a macro you need to type the function:
import test, {Macro} from 'ava';
const macro: Macro = (t, input: string, expected: number) => {
t.is(eval(input), expected);
};
macro.title = (providedTitle: string, input: string, expected: number) => `${providedTitle} ${input} = ${expected}`.trim();
test(macro, '2 + 2', 4);
test(macro, '2 * 3', 6);
test('providedTitle', macro, '3 * 3', 9);
You'll need a different type if you're expecting your macro to be used with a callback test:
import test, {CbMacro} from 'ava';
const macro: CbMacro = t => {
t.pass();
setTimeout(t.end, 100);
};
test.cb(macro);
Typing t.context
By default, the type of t.context
will be the empty object ({}
). AVA exposes an interface TestInterface<Context>
which you can use to apply your own type to t.context
. This can help you catch errors at compile-time:
import anyTest, {TestInterface} from 'ava';
const test = anyTest as TestInterface<{foo: string}>;
test.beforeEach(t => {
t.context = {foo: 'bar'};
});
test.beforeEach(t => {
t.context.foo = 123; // error: Type '123' is not assignable to type 'string'
});
test.serial.cb.failing('very long chains are properly typed', t => {
t.context.fooo = 'a value'; // error: Property 'fooo' does not exist on type ''
});
test('an actual test', t => {
t.deepEqual(t.context.foo.map(c => c), ['b', 'a', 'r']); // error: Property 'map' does not exist on type 'string'
});
You can also type the context when creating macros:
import anyTest, {Macro, TestInterface} from 'ava';
interface Context {
foo: string
}
const test = anyTest as TestInterface<Context>;
const macro: Macro<Context> = (t, expected: string) => {
t.is(t.context.foo, expected);
};
test.beforeEach(t => {
t.context = {foo: 'bar'};
});
test('foo is bar', macro, 'bar');
Note that, despite the type cast above, when executing t.context
is an empty object unless it's assigned.