Adds example for demonstrating Replace Conditional with Polymorphism refactoring

Author: mscottford

code/03-reducing-complexity/03-important-refactorings/03-replace-conditional-with-polymorphism/README.md

@@ -0,0 +1,9 @@
+# Sample for Replace Conditional with Polymorphism Refactoring
+
+The `calculator/index.js` contains the original implementation that uses a conditional to determine the operation to perform. The file `calculator/index.refactored.js` contains that uses polymorphism to separate the different operations.
+
+The same set of tests are used to evaluate the correctness of each file. These are defined in `calculator/calculatorTests.js`. The `index.test.js` and `index.refactored.test.js` files import the appropriate `Calculator` instance to test.
+
+## Running the Tests
+
+Assuming that you have `node` version 20.5.1 or higher, and at least version 9.8.0 of `npm`, then you should be able to run the tests with `npm run test` after installing the dependencies with `npm install`.

code/03-reducing-complexity/03-important-refactorings/03-replace-conditional-with-polymorphism/calculator/.gitignore

@@ -0,0 +1,130 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional stylelint cache
+.stylelintcache
+
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variable files
+.env
+.env.development.local
+.env.test.local
+.env.production.local
+.env.local
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+out
+
+# Nuxt.js build / generate output
+.nuxt
+dist
+
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
+# vuepress build output
+.vuepress/dist
+
+# vuepress v2.x temp and cache directory
+.temp
+.cache
+
+# Docusaurus cache and generated files
+.docusaurus
+
+# Serverless directories
+.serverless/
+
+# FuseBox cache
+.fusebox/
+
+# DynamoDB Local files
+.dynamodb/
+
+# TernJS port file
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+.vscode-test
+
+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*

code/03-reducing-complexity/03-important-refactorings/03-replace-conditional-with-polymorphism/calculator/calculatorTests.js

@@ -0,0 +1,213 @@
+export default function calculatorTests(Calculator, name) {
+  describe(`${name} Calculator`, () => {
+    describe('add', () => {
+      test('with two integers', () => {
+        const calculator = new Calculator();
+        calculator.execute('add 5 3');
+        expect(calculator.result).toBe(8);
+      });
+
+      test('with two floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('add 5.5 3.3');
+        expect(calculator.result).toBe(8.8);
+      });
+
+      test('with two negative numbers', () => {
+        const calculator = new Calculator();
+        calculator.execute('add -5 -3');
+        expect(calculator.result).toBe(-8);
+      });
+
+      test('with first number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('add -5 3');
+        expect(calculator.result).toBe(-2);
+      });
+
+      test('with second number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('add 5 -3');
+        expect(calculator.result).toBe(2);
+      })
+
+      test('with two negative floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('add -5.5 -3.3');
+        expect(calculator.result).toBe(-8.8);
+      })
+    });
+
+    describe('subtract', () => {
+      test('with two integers', () => {
+        const calculator = new Calculator();
+        calculator.execute('subtract 5 3');
+        expect(calculator.result).toBe(2);
+      });
+
+      test('with two floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('subtract 5.5 3.3');
+        expect(calculator.result).toBe(2.2);
+      });
+
+      test('with two negative numbers', () => {
+        const calculator = new Calculator();
+        calculator.execute('subtract -5 -3');
+        expect(calculator.result).toBe(-2);
+      });
+
+      test('with first number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('subtract -5 3');
+        expect(calculator.result).toBe(-8);
+      });
+
+      test('with second number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('subtract 5 -3');
+        expect(calculator.result).toBe(8);
+      })
+
+      test('with two negative floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('subtract -5.5 -3.3');
+        expect(calculator.result).toBe(-2.2);
+      })
+    });
+
+    describe('multiply', () => {
+      test('with two integers', () => {
+        const calculator = new Calculator();
+        calculator.execute('multiply 5 3');
+        expect(calculator.result).toBe(15);
+      });
+
+      test('with two floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('multiply 5.5 3.3');
+        expect(calculator.result).toBe(18.15);
+      });
+
+      test('with two negative numbers', () => {
+        const calculator = new Calculator();
+        calculator.execute('multiply -5 -3');
+        expect(calculator.result).toBe(15);
+      });
+
+      test('with first number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('multiply -5 3');
+        expect(calculator.result).toBe(-15);
+      });
+
+      test('with second number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('multiply 5 -3');
+        expect(calculator.result).toBe(-15);
+      })
+
+      test('with two negative floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('multiply -5.5 -3.3');
+        expect(calculator.result).toBe(18.15);
+      })
+    });
+
+    describe('divide', () => {
+      test('with two integers', () => {
+        const calculator = new Calculator();
+        calculator.execute('divide 5 3');
+        expect(calculator.result).toBeCloseTo(1.6666666666666667);
+      });
+
+      test('with two floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('divide 5.5 3.3');
+        expect(calculator.result).toBeCloseTo(1.6666666666666667);
+      });
+
+      test('with two negative numbers', () => {
+        const calculator = new Calculator();
+        calculator.execute('divide -5 -3');
+        expect(calculator.result).toBeCloseTo(1.6666666666666667);
+      });
+
+      test('with first number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('divide -5 3');
+        expect(calculator.result).toBeCloseTo(-1.6666666666666667);
+      });
+
+      test('with second number negative', () => {
+        const calculator = new Calculator();
+        calculator.execute('divide 5 -3');
+        expect(calculator.result).toBeCloseTo(-1.6666666666666667);
+      })
+
+      test('with two negative floats', () => {
+        const calculator = new Calculator();
+        calculator.execute('divide -5.5 -3.3');
+        expect(calculator.result).toBeCloseTo(1.6666666666666667);
+      })
+    });
+
+    describe('multiple operations', () => {
+      test('adds using initial value', () => {
+        const calculator = new Calculator(5);
+        calculator.execute('add 5');
+        calculator.execute('add 3');
+        expect(calculator.result).toBe(13);
+      });
+
+      test('adds ignoring initial value', () => {
+        const calculator = new Calculator(5);
+        calculator.execute('add 5 3');
+        calculator.execute('add 5');
+        expect(calculator.result).toBe(13);
+      });
+
+      test('subtracts using initial value', () => {
+        const calculator = new Calculator(7);
+        calculator.execute('subtract 5');
+        calculator.execute('subtract 3');
+        expect(calculator.result).toBe(-1);
+      });
+
+      test('subtracts ignoring initial value', () => {
+        const calculator = new Calculator(7);
+        calculator.execute('subtract 5 3');
+        calculator.execute('subtract 5');
+        expect(calculator.result).toBe(-3);
+      });
+
+      test('multiplies using initial value', () => {
+        const calculator = new Calculator(2);
+        calculator.execute('multiply 5');
+        calculator.execute('multiply 3');
+        expect(calculator.result).toBe(30);
+      });
+
+      test('multiplies ignoring initial value', () => {
+        const calculator = new Calculator(2);
+        calculator.execute('multiply 5 3');
+        calculator.execute('multiply 5');
+        expect(calculator.result).toBe(75);
+      });
+
+      test('divides using initial value', () => {
+        const calculator = new Calculator(100);
+        calculator.execute('divide 5');
+        calculator.execute('divide 3');
+        expect(calculator.result).toBeCloseTo(6.666666666666667);
+      });
+
+      test('divides ignoring initial value', () => {
+        const calculator = new Calculator(100);
+        calculator.execute('divide 10 5');
+        calculator.execute('divide 3');
+        expect(calculator.result).toBeCloseTo(0.666666666666667);
+      });
+    });
+  });
+}