🔢toBeNaN

Determine if your number is not a number

As the joke goes...

typeof NaN === "number"

... as in, the NaN float value is considered a number. However, toBe assertions will fail if you try to expect some value toBe(NaN) . This assertion will provide proof that your actual value is, in fact, a NaN value.

expect(NaN).toBeNaN(); // passes
expect(1.0).not.toBeNaN(); // passes

// compile time error, will be reported when the suite is run
expect(new Vec3()).not.toBeNaN();

If this method is called with anything other than a f32 | f64 type, it will result in a compile time error.

This method is safe to use with jest portably.