chapter 03: copy code from chapter 02 to the chapter 03 folder in order to continue with the book

Author: devcorpio

chapter_03-using-stubs-to-break-dependencies/LogAn/ArgumentError.js

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+class ArgumentError extends Error {}
+
+module.exports = ArgumentError;

chapter_03-using-stubs-to-break-dependencies/LogAn/logAnalyzer.js

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+const ArgumentError = require('./ArgumentError');
+
+function logAnalyzer() {
+    /**
+     * @type {boolean}
+     */
+    let wasLastFileNameValid;
+
+    /**
+     * @return {boolean}
+     */
+    function getWasLastFileNameValid() {
+        return wasLastFileNameValid;
+    }
+
+    /**
+     * @param {string} fileName
+     * @return {boolean}
+     */
+    function isValidLogFileName(fileName) {
+        wasLastFileNameValid = false;
+
+        if (fileName === '') {
+            throw new ArgumentError('filename has to be provided');
+        }
+
+        if (!fileName.toUpperCase().endsWith('.SLF')) {
+            return false;
+        }
+
+        wasLastFileNameValid = true;
+        return true;
+    }
+
+    return {
+        getWasLastFileNameValid,
+        isValidLogFileName,
+    };
+}
+
+module.exports = logAnalyzer;

chapter_03-using-stubs-to-break-dependencies/LogAn/logAnalyzer.test.js

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+const logAnalyzer = require('./logAnalyzer');
+
+let logAnalyzerInstance;
+beforeEach(() => {
+    logAnalyzerInstance = logAnalyzer();
+});
+
+describe.each([
+    ['johndoe.js', false],
+    ['johndoe.slf', true],
+    ['johndoe.SLF', true],
+])('isValidLogFileName("%s"))', (fileName, expected) => {
+    it(`bad extension returns ${expected}`, () => {
+        const result = logAnalyzerInstance.isValidLogFileName(fileName);
+        expect(result).toBe(expected);
+    });
+});
+
+describe('isValidLogFileName', () => {
+    it('empty filename throws error', () => {
+        function emptyLogFileName() {
+            logAnalyzerInstance.isValidLogFileName('');
+        }
+
+        expect(emptyLogFileName).toThrow('filename has to be provided');
+    });
+
+    /**
+     * an example of state-based testing
+     */
+    it.each`
+        fileName         | expected
+        ${'johndoe.foo'} | ${false}
+        ${'johndoe.slf'} | ${true}
+    `(
+        'when called there changes wasLastFileNameValid that returns $expected',
+        ({ fileName, expected }) => {
+            console.log(fileName);
+            logAnalyzerInstance.isValidLogFileName(fileName);
+            const result = logAnalyzerInstance.getWasLastFileNameValid();
+
+            expect(result).toBe(expected);
+        }
+    );
+});