replace jest with ava

node_modules/concordance/README.md

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+# concordance
+
+Compare, format, diff and serialize any JavaScript value. Built for Node.js 6
+and above.
+
+## Behavior
+
+Concordance recursively describes JavaScript values, whether they're booleans or
+complex object structures. It recurses through all enumerable properties, list
+items (e.g. arrays) and iterator entries.
+
+The same algorithm is used when comparing, formatting or diffing values. This
+means Concordance's behavior is consistent, no matter how you use it.
+
+### Comparison details
+
+* [Object wrappers](https://github.com/getify/You-Dont-Know-JS/blob/master/types%20%26%20grammar/ch3.md#boxing-wrappers)
+  are compared both as objects and unwrapped values. Thus Concordance always
+  treats `Object(1)` as different from `1`.
+* `-0` is distinct from `0`.
+* `NaN` equals `NaN`.
+* The `Argument` values can be compared to a regular array.
+* `Error` names and messages are always compared, even if these are not
+  enumerable properties.
+* `Function` values are compared by identity only. Names are always formatted
+  and serialized.
+* `Global` objects are considered equal.
+* `Map` keys and `Set` items are compared in-order.
+* `Object` string properties are compared according to the [traversal order](http://2ality.com/2015/10/property-traversal-order-es6.html).
+  Symbol properties are compared by identity.
+* `Promise` values are compared by identity only.
+* `Symbol` values are compared by identity only.
+* Recursion stops whenever a circular reference is encountered. If the same
+  cycle is present in the actual and expected values they're considered equal,
+  but they're unequal otherwise.
+
+### Formatting details
+
+Concordance strives to format every aspect of a value that is used for
+comparisons. Formatting is optimized for human legibility.
+
+Strings enjoy special formatting:
+
+* When used as keys, line break characters are escaped
+* Otherwise, multi-line strings are formatted using backticks, and line break
+  characters are replaced by [control pictures](http://graphemica.com/blocks/control-pictures).
+
+Similarly, line breaks in symbol descriptions are escaped.
+
+### Diffing details
+
+Concordance tries to minimize diff lines. This is difficult with object values,
+which may have similar properties but a different constructor. Multi-line
+strings are compared line-by-line.
+
+### Serialization details
+
+Concordance can serialize any value for later use. Deserialized values can be
+compared to each other or to regular JavaScript values. The deserialized
+value should be passed as the **actual** value to the comparison and diffing
+methods. Certain value comparisons behave differently when the **actual** value
+is deserialized:
+
+* `Argument` values can only be compared to other `Argument` values.
+* `Function` values are compared by name.
+* `Promise` values are compared by their constructor and additional enumerable
+  properties, but not by identity.
+* `Symbol` values are compared by their string serialization. [Registered](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Symbol#Shared_symbols_in_the_global_symbol_registry)
+   and [well-known symbols](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Symbol#Well-known_symbols)
+   will never equal symbols with similar descriptions.