[N8N-4339] Unify all Cron-specific code. Improve typing, and add tests. (#3887)

packages/workflow/test/Cron.test.ts

@@ -0,0 +1,75 @@
+import { toCronExpression } from "../src/Cron"
+
+describe('Cron', () => {
+  describe('toCronExpression', () => {
+    test('should generate a valid cron for `everyMinute` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyMinute',
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] \* \* \* \* \*$/)
+    })
+
+    test('should generate a valid cron for `everyHour` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyHour',
+        minute: 11,
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] 11 \* \* \* \*$/)
+    })
+
+    test('should generate a valid cron for `everyX[minutes]` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyX',
+        unit: 'minutes',
+        value: 42,
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] \*\/42 \* \* \* \*$/)
+    })
+
+    test('should generate a valid cron for `everyX[hours]` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyX',
+        unit: 'hours',
+        value: 3,
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] 0 \*\/3 \* \* \*$/)
+    })
+
+    test('should generate a valid cron for `everyDay` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyDay',
+        hour: 13,
+        minute: 17,
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] 17 13 \* \* \*$/)
+    })
+
+    test('should generate a valid cron for `everyWeek` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyWeek',
+        hour: 13,
+        minute: 17,
+        weekday: 4,
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] 17 13 \* \* 4$/)
+    })
+
+    test('should generate a valid cron for `everyMonth` triggers', () => {
+      const expression = toCronExpression({
+        mode: 'everyMonth',
+        hour: 13,
+        minute: 17,
+        dayOfMonth: 12,
+      })
+      expect(expression).toMatch(/^[1-6]?[0-9] 17 13 12 \* \*$/)
+    })
+
+    test('should trim custom cron expressions', () => {
+      const expression = toCronExpression({
+        mode: 'custom',
+        cronExpression: ' 0 9-17 * * * ',
+      })
+      expect(expression).toEqual('0 9-17 * * *')
+    })
+  })
+})