1 files changed, 80 insertions, 0 deletions
diff --git a/date-fns/src/compareDesc/test.ts b/date-fns/src/compareDesc/test.ts
new file mode 100644
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+++ b/date-fns/src/compareDesc/test.ts
@@ -0,0 +1,80 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'assert'
+import compareDesc from '.'
+
+describe('compareDesc', function() {
+  it('returns 0 if the given dates are equal', function() {
+    const result = compareDesc(
+      new Date(1989, 6 /* Jul */, 10),
+      new Date(1989, 6 /* Jul */, 10)
+    )
+    assert(result === 0)
+  })
+
+  it('returns 1 if the first date is before the second one', function() {
+    const result = compareDesc(
+      new Date(1987, 1 /* Feb */, 11),
+      new Date(1989, 6 /* Jul */, 10)
+    )
+    assert(result === 1)
+  })
+
+  it('returns -1 if the first date is after the second one', function() {
+    const result = compareDesc(
+      new Date(1989, 6 /* Jul */, 10),
+      new Date(1987, 1 /* Feb */, 11)
+    )
+    assert(result === -1)
+  })
+
+  it('sorts the dates array in the reverse chronological order when function is passed as the argument to Array.prototype.sort()', function() {
+    const unsortedArray = [
+      new Date(1995, 6 /* Jul */, 2),
+      new Date(1987, 1 /* Feb */, 11),
+      new Date(1989, 6 /* Jul */, 10)
+    ]
+
+    const sortedArray = [
+      new Date(1995, 6 /* Jul */, 2),
+      new Date(1989, 6 /* Jul */, 10),
+      new Date(1987, 1 /* Feb */, 11)
+    ]
+
+    unsortedArray.sort(compareDesc)
+    const result = unsortedArray
+
+    assert.deepStrictEqual(result, sortedArray)
+  })
+
+  it('accepts timestamps', function() {
+    const result = compareDesc(
+      new Date(1987, 1 /* Feb */, 11).getTime(),
+      new Date(1989, 6 /* Jul */, 10).getTime()
+    )
+    assert(result === 1)
+  })
+
+  it('returns NaN if the first date is `Invalid Date`', function() {
+    const result = compareDesc(new Date(NaN), new Date(1989, 6 /* Jul */, 10))
+    assert(isNaN(result))
+  })
+
+  it('returns NaN if the second date is `Invalid Date`', function() {
+    const result = compareDesc(new Date(1989, 6 /* Jul */, 10), new Date(NaN))
+    assert(isNaN(result))
+  })
+
+  it('returns NaN if the both dates are `Invalid Date`', function() {
+    const result = compareDesc(new Date(1989, 6 /* Jul */, 10), new Date(NaN))
+    assert(isNaN(result))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function() {
+    //@ts-expect-error
+    assert.throws(compareDesc.bind(null), TypeError)
+    //@ts-expect-error
+    assert.throws(compareDesc.bind(null, 1), TypeError)
+  })
+})