typescript(option): test: wrote tests for filter

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

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

@@ -0,0 +1,47 @@
+import { expect } from 'chai'
+import { constantly } from '@thi.ng/compose'
+import { filter } from './filter'
+import { None, Some } from '../types'
+import { someX } from '../../test/constants'
+
+describe('The filter helper', () => {
+    describe('When the predicate returns true', () => {
+        const predicate = constantly(true)
+
+        it('should return None when given None', () => {
+            // act
+            const result = filter(predicate, None)
+
+            // assert
+            expect(result).to.equal(None)
+        })
+
+        it('should return Some(x) when given Some(x)', () => {
+            // act
+            const result = filter(predicate, someX)
+
+            // assert
+            expect(result).to.equal(someX)
+        })
+    })
+
+    describe('When the predicate returns false', () => {
+        const predicate = constantly(false)
+
+        it('should return None when given Some', () => {
+            // act
+            const result = filter(predicate, someX)
+
+            // assert
+            expect(result).to.equal(None)
+        })
+
+        it('should return None when given None', () => {
+            // act
+            const result = filter(predicate, None)
+
+            // assert
+            expect(result).to.equal(None)
+        })
+    })
+})

typescript/option/test/constants.ts

@@ -1,2 +1,7 @@
+import { Some } from '../src'
+
 // general value to pass around
 export const x = Symbol('x')
+
+// same as x but for some
+export const someX = Some(x)

typescript/option/tsconfig.json

@@ -8,5 +8,6 @@
         "downlevelIteration": true,
         "target": "es6"
     },
-    "include": ["src", "sandbox", "test"]
+    "include": ["src", "sandbox", "test"],
+    "exclude": ["dist"]
 }