Releases

Here is a very high level overview of the major releases. See the changelog for more details.

This release includes backwards-incompatible changes. There's a migration guide to help you upgrade.

Drop support for node.js < 6
The main export is now a frozen expect function. To add assertions and install plugins, you must now clone() it first (#517)
Include non-enumerable properties when comparing objects (#482)
to satisfy now compares functions by value. Functions in the spec that are to be executed must now be wrapped in expect.it (#328)
The function type is now modelled as a subtype of object. This means that all assertions defined for object, such as to have properties, also work for functions now (#448)
Drop compatibility with pre-10.10.0 diff objects. This will mainly affect older plugins (#407)
Remove support for expect.async (#566)
Remove long-deprecated support for this.subject etc. in assertion handlers (#567)

Assertions are now declared with explicit type requirements for the arguments as part of the pattern. This is a breaking change that removes support for the old addAssertion syntax where the subject type(s) were passed as the first argument. See addAssertion for more information.
The to be >, to be >=, to be <, and to be <= assertions have been removed as they clashed with the new type syntax. Please use the fully spelled-out variants: to be greater than, to be less than or equal to, etc.
The [not] to begin with, [not] to end with, and [not] to contain assertions now require strings as the needle(s). Previously they supported any type, which would then be stringified.
Inside an assertion you can now access the errorMode, shift, flags, alternations properties etc. via the expect passed to the assertion. They can still be accessed via this as previously, but that is deprecated. (This change actually debuted in 9.12.0).
The when passed as parameter(s) to, when called with, when decoded as assertions can now be used standalone, ie. without delegating the result to another assertion in the same expect call. In that case they will provide the result as the fulfillment value of the promise.

Build all error messages lazily. This is an internal refactoring that makes it possible to generate very different output in the text, Ansi, and HTML modes using the magicpen raw feature. This change mostly affects plugins, and we have updated all the official plugins accordingly, so please upgrade those to the latest version when you upgrade to Unexpected 9.
Made it possible to tweak the default error message when creating assertions. See addAssertion for more information.
Expanded the to have message assertion defined for Error instances to allow matching a serialization other than plain text: to have ansi message, to have html message.
The to contain assertion defined for strings: When the assertion fails, display a "diff" where partial matches are highlighted.

All errors originating from assertions are now instances of UnexpectedError, which can be manipulated before being serialized.
Error messages and diffs are now built lazily, improving performance.
Unexpected now detects created promises that were never returned and fails synchronously. This will uncover some extremely nasty bugs where the test suite succeeds when it should actually fail. This feature only works in Mocha and Jasmine.
Deprecated error.output, please use error.getErrorMessage() instead.
Deprecated error.label, please use error.getLabel() instead.
when decoded as, when called with, when passed as parameter to, when passed as parameters to: Require the 4th argument to be a string specifying an assertion. Previously a function was also allowed, which turned out to be error prone. This also affects all plugins that use the internal function Assertion.prototype.shift to delegate to other assertions.
Nested error mode: Don't repeat the subject when it takes up multiple lines and is identical to the parent subject.
Added a new bubbleThrough error mode that will make the error bubble all the way to the top, mainly useful internally.
Added to error assertion.
Minor bugfixes and output tweaks.

Support for asynchronous assertions using promises. All built-in assertions that delegate to other assertions (such as to satisfy) have been rewritten to support this. The change is fully backwards compatible.
Removed support for the to be an array of and to be an array of (strings|numbers|...) assertions. There are better and more flexible alternatives.
Renamed assertions so that the subject type isn't mentioned in the assertion name. The old names are kept around as aliases for now. These assertions are affected:
- to be an array whose items satisfy => to have items satisfying
- to be an (object|hash|map) whose keys satisfy => to have keys satisfying
- to be an (object|hash|map) whose values satisfy => to have values satisfying Also, these 3 assertions no longer pass for empty collections.
New when passed as parameter to constructor and when passed as parameter to async "adverbial" assertions.
New when decoded as "adverbial" assertion for Buffer instances.
New to have message assertion defined for Error instances.
A lot of output improvements and minor tweaks.

New documentation and corresponding site.
Use Object.is/the SameValue algorithm when checking equality of primitive values (the to be and to equal assertions).
Tweaked the output of numerous assertions.
Constrained to be empty and to have length to only work with strings and array-like objects.
Renamed the arrayLike type to array-like.
Changed style names and added theming support (mostly internal).
Removed grammatically incorrect assertions.

Added type system for assertion subjects.
Use magicpen for all generating all output. No longer rely on the tests runner to render diffs.

Hand an expect function to custom assertions.
Added the ability for an assertion to control how the error message of nested expect calls are formatted.