Description

When formatting a TimeSpan we currently combine the second and millisecond parts, such that TimeSpan.FromSeconds(1.5) is formatted as 1.500s.

When the time span is less than 1 second we could improve formatting by outputting the value in milliseconds instead.

Complete minimal example reproducing the issue

Func<Task> act = () => Task.Delay(50.Milliseconds());

await act.Should().CompleteWithinAsync(1.Milliseconds());

Expected behavior:

Expected task to complete within 1ms.

Actual behavior:

Expected task to complete within 0.001s.