Added tests

tests/lens.test.js

@@ -1,15 +1,18 @@
 /* global describe, it, beforeEach */
 import expect from 'expect';
-import { compose, view, set, At } from '../src/lens';
+import { compose, view, set, At, Path, over } from '../src/lens';
 
 describe('At', function() {
   let lens;
   beforeEach(function() {
-    lens = compose(At(0, []), At("hello"));
+    lens = compose(
+      At(0, []),
+      At('hello')
+    );
   });
 
   it('instantiates objects of the correct type at each path', function() {
-    expect(set(lens, "world", undefined)).toEqual([{hello: 'world'}]);
+    expect(set(lens, 'world', undefined)).toEqual([{ hello: 'world' }]);
   });
 
   it('set-get: view retrievs what set put in', function() {
@@ -19,7 +22,120 @@ describe('At', function() {
   });
 
   it('get-set: If you set focus to the same value it has, the whole does not change', function() {
-    let object = set(lens, "world", undefined);
-    expect(set(lens, "world", object)).toBe(object);
+    let object = set(lens, 'world', undefined);
+    expect(set(lens, 'world', object)).toBe(object);
   });
-});
+});
+
+describe('Path', () => {
+  let userNameLens;
+  let result;
+  beforeEach(() => {
+    userNameLens = Path(['user', 'name']);
+  });
+  describe('set', () => {
+    describe('when value is an object', () => {
+      let value = { user: { name: 'Bob' } };
+      beforeEach(() => {
+        result = set(userNameLens, 'Bobby', value);
+      });
+      it('creates a new context at root', () => {
+        expect(result).not.toBe(value);
+      });
+      it('creates a new context in middle location', () => {
+        expect(result.user).not.toBe(value.user);
+      });
+      it('applies the value at focus', () => {
+        expect(result).toHaveProperty(['user', 'name'], 'Bobby');
+      });
+    });
+    describe('when value is undefined', () => {
+      beforeEach(() => {
+        result = set(userNameLens, 'John', undefined);
+      });
+      it('creates context', () => {
+        expect(result).toMatchObject({
+          user: {
+            name: 'John'
+          }
+        });
+      });
+    });
+  });
+  describe('view', () => {
+    describe('when value is present', () => {
+      beforeEach(() => {
+        result = view(userNameLens, { user: { name: 'Frank' } });
+      });
+      it('returns the value at focus', () => {
+        expect(result).toBe('Frank');
+      });
+    });
+    describe('when value is not present', () => {
+      beforeEach(() => {
+        result = view(userNameLens, undefined);
+      });
+      it('returns undefined', () => {
+        expect(result).toBeUndefined();
+      });
+    });
+  });
+  describe('over', () => {
+    describe('when value is present', () => {
+      let value = { user: { name: 'George' } };
+      beforeEach(() => {
+        result = over(userNameLens, s => s.toUpperCase(), value);
+      });
+      it('applies the function to the focus', () => {
+        expect(result).toHaveProperty(['user', 'name'], 'GEORGE');
+      });
+    });
+    describe('when value is not present', () => {
+      let value = undefined;
+      beforeEach(() => {
+        result = over(userNameLens, (s = '') => s.toUpperCase(), value);
+      });
+      it('creates context for the value', () => {
+        expect(result).toMatchObject({
+          user: {
+            name: ''
+          }
+        });
+      });
+    });
+  });
+  describe('composition with At', () => {
+    let lens;
+    beforeEach(() => {
+      lens = compose(
+        At(0, []),
+        userNameLens
+      );
+    });
+    describe('set', () => {
+      beforeEach(() => {
+        result = set(lens, 'Will');
+      });
+      it('creates composed context', () => {
+        expect(result).toMatchObject([{ user: { name: 'Will' } }]);
+      });
+    });
+    describe('view', () => {
+      beforeEach(() => {
+        result = view(lens, [{ user: { name: 'Rob' } }]);
+      });
+      it('returns value from focus', () => {
+        expect(result).toBe('Rob');
+      });
+    });
+    describe('over', () => {
+      let value = [{ user: { name: 'john' } }];
+      beforeEach(() => {
+        result = over(lens, s => s.toUpperCase(), value);
+      });
+      it('creates the context', () => {
+        expect(result).toMatchObject([{ user: { name: 'JOHN' } }]);
+      });
+    });
+  });
+});