test: add tests for validateEmail function

src/validateEmail.test.js

@@ -2,19 +2,57 @@
 
 describe(`Function 'validateEmail':`, () => {
   const validateEmail = require('./validateEmail');
+  const cases = [
+    {
+      input: 'test@mail.com', expected: true,
+    },
+    {
+      input: 't@q.c', expected: true,
+    },
+    {
+      input: 'test838@gmail.com', expected: true,
+    },
+  ];
 
   it(`should be declared`, () => {
     expect(validateEmail).toBeInstanceOf(Function);
   });
 
   it(`should return boolean`, () => {
+    expect(typeof validateEmail('test838@gmail.com')).toBe('boolean');
+  });
+
+  it(`should return 'true' for all valid emails`, () => {
+    cases.forEach(({ input, expected }) => {
+      expect(validateEmail(input)).toBe(expected);
+    });
+  });
+
+  it(`should return 'false' for email with not allowed char`, () => {
+    expect(validateEmail('test!838@gmail.com')).toBe(false);
+  });
+
+  it(`should return 'false' for email with double dots`, () => {
+    expect(validateEmail('test..838@gmail.com')).toBe(false);
+  });
+
+  it(`should return 'false' if email starts with '.'`, () => {
+    expect(validateEmail('.test838@gmail.com')).toBe(false);
+  });
 
+  it(`should return 'false' for emails without '@'`, () => {
+    expect(validateEmail('test838gmail.com')).toBe(false);
   });
 
-  it(`should return 'true' for the valid email`, () => {
-    expect(validateEmail('test838@gmail.com.'))
-      .toBeTruthy();
+  it(`should return 'false' for email without dot in domain part`, () => {
+    expect(validateEmail('false@email')).toBe(false);
   });
 
-  // write more tests here
+  it(`should return 'false' if '.' is directly before '@'`, () => {
+    expect(validateEmail('false.@email.com')).toBe(false);
+  });
+
+  it(`should return 'false' if '.' is directly after '@'`, () => {
+    expect(validateEmail('false@.email.com')).toBe(false);
+  });
 });