diff --git a/test/set-new-cycle-start.spec.js b/test/set-new-cycle-start.spec.js
new file mode 100644
index 0000000..973415c
--- /dev/null
+++ b/test/set-new-cycle-start.spec.js
@@ -0,0 +1,78 @@
+import chai from 'chai'
+import dirtyChai from 'dirty-chai'
+import maybeSetNewCycleStart from '../lib/set-new-cycle-start'
+
+const expect = chai.expect
+chai.use(dirtyChai)
+
+describe('maybeSetNewCycleStart', () => {
+  function getFixtures() {
+    const cycleDay = {
+      date: '2020-01-01',
+      isCycleStart: true,
+      bleeding: {
+        value: 2,
+        exclude: false
+      }
+    }
+
+    const mensesDaysAfter = [
+      {
+        date: '2020-01-04',
+        isCycleStart: false,
+        value: {
+          bleeding: {
+            value: 2,
+            exclude: false
+          }
+        }
+      },
+      {
+        date: '2020-01-03',
+        isCycleStart: false,
+        value: {
+          bleeding: {
+            value: 2,
+            exclude: false
+          }
+        }
+      },
+      {
+        date: '2020-01-02',
+        isCycleStart: false,
+        value: {
+          bleeding: {
+            value: 2,
+            exclude: false
+          }
+        }
+      }
+    ]
+    return [cycleDay, mensesDaysAfter]
+  }
+
+  const checkIsMensesStart = cycleDay => {
+    if (cycleDay.date === '2020-01-02') return true
+  }
+
+  it('sets new cycle start when first day of period deleted', () => {
+    const deletedBleedingValue = null
+
+    const [dayWithDeletedBleeding, mensesDaysAfter] = getFixtures()
+
+    maybeSetNewCycleStart({
+      val: deletedBleedingValue,
+      cycleDay: dayWithDeletedBleeding,
+      mensesDaysAfter,
+      checkIsMensesStart
+    })
+    expect(dayWithDeletedBleeding.isCycleStart).to.be.false()
+    expect(dayWithDeletedBleeding.bleeding).to.be.null()
+    expect(mensesDaysAfter[2].isCycleStart).to.be.true()
+  })
+  it('sets new cycle start when first day of period excluded', () => {})
+  it('does not set new cycle start when other day of period deleted', () => {})
+  it('does not set new cycle start when other day of period excluded', () => {})
+  it('works when there are no followiing bleeding days', () => {})
+  it('works when the following bleeding days are already the start of a new cycle', () => {})
+})
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