Using Matchers

The simplest way to test a value is with exact equality.

test('two plus two is four', () => {
  expect(2 + 2).equal(4);
});

In this code, expect(2+2) returns an "Value" object. You typically won't do much with these objects except call matchers on them. In this code, .equal(4) is the matcher. When Jest runs, it tracks all the failing matchers so that it can print out nice error messages for you.

Not

not matcher can reverse the matching results of all subsequent matcher statements.

expect(1).not.equal(2); // success
expect(1).not.equal(1); // fail

Equal

In the most condition, equal is similar as ==, you can use this matcher to compare i32 | i64 | u32 | u64 | f32 | f64 | string just like ==. What's more, it can also be used to compare some inner type, such as Array | Map | Set.

However, Class and Interface cannot be compared directly now.

notEqual is the opposite of equal

Numbers

Most ways of comparing numbers have matcher equivalents, like equal, greaterThan, greaterThanOrEqual, lessThan, lessThanOrEqual.

Specially, for float type, use closeTo instead of equal to avoid rounding error.

Nullable

isNull and notNull matchers can be used to a nullable object. Of course, you can also use equal and notEqual to do same thing with explicit generic declaration expect<T | null>()

Typing

isa and isExactly matchers can be used to compare typing.

In Assemblyscript, a variable has 2 kinds of types: the defined type and the runtime type. For example, when Ext extends Base, a variable declared as type Base may actually be of type Ext at runtime.

• isa will check whether runtime type of given value is instance of expected type. In previous example, the runtime type of variable is instance of both Base and Ext.
• isExactly will check whether runtime type of give value is exactly same as expected type. In previous example, the runtime type of variable is exactly Ext but not Base.