Fix test file name spelling

test/period-length.spec.js

@@ -0,0 +1,64 @@
+import chai from 'chai'
+import { AssertionError } from 'assert'
+
+import periodInfo from '../lib/period-length'
+
+const expect = chai.expect
+
+describe('getPeriodLengthStats', () => {
+  it('works for a simple odd-numbered array', () => {
+    const periodLengths = [99, 5, 1, 2, 100]
+    const result = periodInfo(periodLengths)
+    const expectedResult = {
+      minimum: 1,
+      maximum: 100,
+      mean: 41.4,
+      median: 5,
+      stdDeviation: 53.06
+    }
+    expect(result).to.eql(expectedResult)
+  })
+
+  it('works for a simple even-numbered array', () => {
+    const periodLengths = [4, 1, 15, 2, 20, 5]
+    const result = periodInfo(periodLengths)
+    const expectedResult = {
+      minimum: 1,
+      maximum: 20,
+      mean: 7.83,
+      median: 4.5,
+      stdDeviation: 7.78
+    }
+    expect(result).to.eql(expectedResult)
+  })
+  it('works for an one-element array', () => {
+    const periodLengths = [42]
+    const result = periodInfo(periodLengths)
+    const expectedResult = {
+      minimum: 42,
+      maximum: 42,
+      mean: 42,
+      median: 42,
+      stdDeviation: null
+    }
+    expect(result).to.eql(expectedResult)
+  })
+  describe('when args are wrong', () => {
+    it('throws when arg object is an empty array', () => {
+      const periodLengths = []
+      expect(() => periodInfo(periodLengths).to.throw(AssertionError))
+    })
+    it('throws when arg object is not in right format', () => {
+      const wrongObject = { hello: 'world' }
+      expect(() => periodInfo(wrongObject).to.throw(AssertionError))
+    })
+    it('throws when arg array contains a string', () => {
+      const wrongElement = [4, 1, 15, '2', 20, 5]
+      expect(() => periodInfo(wrongElement).to.throw(AssertionError))
+    })
+    it('throws when arg array contains a NaN', () => {
+      const wrongElement = [4, 1, 15, NaN, 20, 5]
+      expect(() => periodInfo(wrongElement).to.throw(AssertionError))
+    })
+  })
+})