Moves out the tests for getCycleDayNumber and organises them

test/get-cycle-day-number.spec.js

@@ -0,0 +1,59 @@
+import chai from 'chai'
+import dirtyChai from 'dirty-chai'
+import cycleModule from '../lib/cycle'
+
+const { expect } = chai
+chai.use(dirtyChai)
+
+const simpleCycleStarts = [
+  { date: '2018-05-09' },
+  { date: '2018-05-03'},
+]
+
+describe('getCycleDayNumber', () => {
+  it('works for a date in the current cycle', () => {
+    const cycleStartsSortedByDate = simpleCycleStarts
+    const date = '2018-05-17'
+    const { getCycleDayNumber } = cycleModule({ cycleStartsSortedByDate })
+
+    expect(getCycleDayNumber(date)).to.eql(9)
+  })
+
+  it('works for a date which is not in the current cycle', () => {
+    const cycleStartsSortedByDate = [
+      { date: '2018-05-13' },
+      { date: '2018-04-10'}
+    ]
+    const date = '2018-04-27'
+    const { getCycleDayNumber } = cycleModule({ cycleStartsSortedByDate })
+
+    expect(getCycleDayNumber(date)).to.eql(18)
+  })
+
+  it('works for a date which is the first and only day in cycle', () => {
+    const cycleStartsSortedByDate = [
+      { date: '2018-05-13' }
+    ]
+    const date = '2018-05-13'
+    const { getCycleDayNumber } = cycleModule({ cycleStartsSortedByDate })
+
+    expect(getCycleDayNumber(date)).to.eql(1)
+  })
+
+  it('returns null if there are no cycle starts', function () {
+    const cycleStartsSortedByDate = []
+    const date = '2018-05-17'
+    const { getCycleDayNumber } = cycleModule({ cycleStartsSortedByDate })
+
+    expect(getCycleDayNumber(date)).to.be.null()
+  })
+
+  it('returns null if the cycle is longer than the max', function () {
+    const cycleStartsSortedByDate = simpleCycleStarts
+    // we use the default 99 days max length
+    const date = '2018-08-16'
+    const { getCycleDayNumber } = cycleModule({ cycleStartsSortedByDate })
+
+    expect(getCycleDayNumber(date)).to.be.null()
+  })
+})