Use assert for args check

lib/sympto/index.js

@@ -2,6 +2,7 @@ import getTemperatureShift from './temperature'
 import getMucusShift from './mucus'
 import getPreOvulatoryPhase from './pre-ovulatory'
 import { LocalDate } from 'js-joda'
+import assert from 'assert'
 
 export default function ({ cycle, previousCycle }) {
   throwIfArgsAreNotInRequiredFormat(cycle, previousCycle)
@@ -70,23 +71,16 @@ export default function ({ cycle, previousCycle }) {
 }
 
 function throwIfArgsAreNotInRequiredFormat(cycle, previousCycle) {
-  if (!Array.isArray(cycle) || !cycle.length) throw new Error('Please provide all cycle days as array')
-  if (!Array.isArray(previousCycle) || !previousCycle.length) throw new Error('Please provide previous cycle days as array')
-  if (
-    !cycle[0].bleeding || typeof cycle[0].bleeding.value != 'number' ||
-    !previousCycle[0].bleeding || typeof previousCycle[0].bleeding.value != 'number'
-  ) throw new Error('Cycle must start with bleeding')
-
-  if ([cycle, previousCycle].some(cycle => {
-    return cycle.some(day => {
-      if (!day.date) return true
-      try {
-        LocalDate.parse(day.date)
-      } catch(err) {
-        throw new Error('Please provide dates in ISO8601 format')
-      }
-      if (day.temperature && typeof day.temperature.value != 'number') return true
-      if (day.mucus && typeof day.mucus.value != 'number') return true
+  [cycle, previousCycle].forEach(cycle => {
+    assert.ok(Array.isArray(cycle))
+    assert.ok(cycle.length > 0)
+    assert.equal(typeof cycle[0].bleeding, 'object')
+    assert.equal(typeof cycle[0].bleeding.value, 'number')
+    cycle.forEach(day => {
+      assert.equal(typeof day.date, 'string')
+      assert.doesNotThrow(() => LocalDate.parse(day.date))
+      if (day.temperature) assert.equal(typeof day.temperature.value, 'number')
+      if (day.mucus) assert.equal(typeof day.mucus.value, 'number')
     })
-  })) throw new Error('Cycle days are not in correct format')
+  })
 }