fix: add support for null array. (#23)

* fix: add support for null array.

* test: improve coverage

src/createSatisfier.spec.ts

@@ -31,3 +31,15 @@ test('actual should be a complete struct', t => {
   // t.true(s.test({ a: 1 }))
   t.true(s.test({ a: 1, b: 'b' }))
 })
+
+test('expect null', t => {
+  t.true(createSatisfier(null).test(null))
+})
+test('array with number', t => {
+  t.true(createSatisfier([1, 2]).test([1, 2]))
+})
+
+test('array with null', t => {
+  t.true(createSatisfier([null]).test([null]))
+  t.false(createSatisfier([null]).test([1]))
+})

src/createSatisfier.ts

@@ -4,7 +4,7 @@ import { Struct, Expectation, SatisfierExec } from './interfaces'
  * creates a satisfier
  * @param expectation All properties can be a value which will be compared to the same property in `actual`, RegExp, or a predicate function that will be used to check against the property.
  */
-export function createSatisfier<T extends Struct>(expectation: Expectation<T>): {
+export function createSatisfier<T extends Struct = Struct>(expectation: Expectation<T>): {
   test: (actual: T) => boolean;
   exec: (actual: T) => SatisfierExec[] | undefined;
 } {
@@ -50,6 +50,14 @@ function detectDiff(actual, expected, path: string[] = []) {
       })
     }
   }
+  else if (expected === null) {
+    if (expected !== actual)
+      diff.push({
+        path,
+        expected,
+        actual
+      })
+  }
   else if (expectedType === 'boolean' || expectedType === 'number' || expectedType === 'string' || actual === undefined) {
     if (expected !== actual)
       diff.push({
@@ -82,10 +90,11 @@ function detectDiff(actual, expected, path: string[] = []) {
         expected,
         actual
       })
-    else
+    else {
       Object.keys(expected).forEach(k => {
         diff.push(...detectDiff(actual[k], expected[k], path.concat([k])))
       })
+    }
   }
   return diff
 }

src/interfaces.ts

@@ -28,7 +28,7 @@ export type ExpectationHash<T extends Struct = Struct> = {
   [P in keyof T]: ExpectationNode<T[P]> | ExpectationNode<T[P]>[];
 }
 
-export type Struct = StructNode | StructHash | (StructNode | StructHash)[]
+export type Struct = null | StructNode | StructHash | (StructNode | StructHash)[]
 
 export type StructNode = boolean | number | string | object