Placeholder.reason property

A utility placeholder for describing why the check failed.

Signature:

reason: string;

Remarks

A lot of times, your check might me making multiple assertions, or have different errors depending on the context.

Using a reason, you can specify a place in your message for this data to be provided.

You can then "provide" a reason via ExpectMessageBuilder.reason().

Note that if you "provide" a reason, but your string doesn't have a reason placeholder in it- the reason will be attached right before the metadata as Reason: message

Example 1

Lets say we were checking if a value was an array.

new ExpectMessageBuilder(
  `Expected ${place.name} to be an array`
).failureSuffix(`, but ${place.reason}`);

By using a reason, we can provide a bunch of different reasonings for why the value isn't an array:

Expected '5' to be an array, but it was a number
Expected '{...}' to be an array, but it had a non number key
Expected 'nil' to be an array, but it was undefined

Example 2

If you populate a reason at runtime, but don't have a reason in your message, it will still propgate to the message.

new ExpectMessageBuilder(
  `Expected ${place.name} to be an array`
);

Example error:

Expected '5' to be an array
Reason: it was a number

This way, you can add a reason whenever you need it, without needing to find a predefined spot for it in your message.