feat(rules): adds no-if rule

Update no-if.md

Author: Matt Seccafien

README.md

@@ -117,6 +117,7 @@ installations requiring long-term consistency.
 | [no-focused-tests][]         | Disallow focused tests                                            | ![recommended][] |                     |
 | [no-hooks][]                 | Disallow setup and teardown hooks                                 |                  |                     |
 | [no-identical-title][]       | Disallow identical titles                                         | ![recommended][] |                     |
+| [no-if][]                    | Disallow conditional logic                                        |                  |                     |
 | [no-jasmine-globals][]       | Disallow Jasmine globals                                          | ![recommended][] | ![fixable-yellow][] |
 | [no-jest-import][]           | Disallow importing `jest`                                         | ![recommended][] |                     |
 | [no-mocks-import][]          | Disallow manually importing from `__mocks__`                      |                  |                     |
@@ -165,6 +166,7 @@ https://github.com/dangreenisrael/eslint-plugin-jest-formatting
 [no-focused-tests]: docs/rules/no-focused-tests.md
 [no-hooks]: docs/rules/no-hooks.md
 [no-identical-title]: docs/rules/no-identical-title.md
+[no-if]: docs/rules/no-if.md
 [no-jasmine-globals]: docs/rules/no-jasmine-globals.md
 [no-jest-import]: docs/rules/no-jest-import.md
 [no-mocks-import]: docs/rules/no-mocks-import.md

docs/rules/no-if.md

@@ -0,0 +1,53 @@
+# Disallow conditional logic. (no-if)
+
+Conditional logic in tests is usually an indication that a test is attempting to
+cover too much, and not testing the logic it intends to. Each branch of code
+executing within an if statement will usually be better served by a test devoted
+to it.
+
+Conditionals are often used to satisfy the typescript type checker. In these cases, using the
+non-null assertion operator (!) would be best.
+
+## Rule Details
+
+This rule prevents the use of if/ else statements and conditional (ternary)
+operations in tests.
+
+The following patterns are considered warnings:
+
+```js
+it('foo', () => {
+  if ('bar') {
+    // an if statement here is invalid
+    // you are probably testing too much
+  }
+});
+
+it('foo', () => {
+  const bar = foo ? 'bar' : null;
+});
+```
+
+These patterns would not be considered warnings:
+
+```js
+it('foo', () => {
+  // only test the 'foo' case
+});
+
+it('bar', () => {
+  // test the 'bar' case separately
+});
+
+it('foo', () => {
+  function foo(bar) {
+    // nested functions are valid
+    return foo ? bar : null;
+  }
+});
+```
+
+## When Not To Use It
+
+If you do not wish to prevent the use of if statements in tests, you can safely
+disable this rule.

src/__tests__/rules.test.js

@@ -3,7 +3,7 @@ import { resolve } from 'path';
 import { rules } from '../';
 
 const ruleNames = Object.keys(rules);
-const numberOfRules = 33;
+const numberOfRules = 34;
 
 describe('rules', () => {
   it('should have a corresponding doc for each rule', () => {