typescript(option): test: added tests for bind

Signed-off-by: prescientmoon <git@moonythm.dev>

typescript/option/src/helpers/bind.test.ts

@@ -0,0 +1,32 @@
+import { expect } from 'chai'
+import { bind } from './bind'
+import { Some, None } from '../types'
+import { constantly } from '@thi.ng/compose'
+
+describe('The bind helper', () => {
+    it('should return none for any callback when given None', () => {
+        // act
+        const result = bind(Some, None)
+
+        // assert
+        expect(result).to.equal(None)
+    })
+
+    describe('When given Some', () => {
+        it('should return None if the callback returns None', () => {
+            // act
+            const result = bind(constantly(None), Some(3))
+
+            // assert
+            expect(result).to.equal(None)
+        })
+
+        it('should return Some if the callback returns Some', () => {
+            // act
+            const result = bind(x => Some(x + 1), Some(3))
+
+            // assert
+            expect(result).to.equal(Some(4))
+        })
+    })
+})