feat: refactor and test tools steps utilities (#42693)

tools/challenge-helper-scripts/helpers/get-existing-step-nums.test.js

@@ -0,0 +1,74 @@
+const mock = require('mock-fs');
+const { getExistingStepNums } = require('./get-existing-step-nums');
+
+// NOTE:
+// Use `console.log()` before mocking the filesystem or use
+// `process.stdout.write()` instead. There are issues when using `mock-fs` and
+// `require`.
+
+describe('getExistingStepNums helper', () => {
+  it('should return the number portion of the project paths', () => {
+    mock({
+      'mock-project': {
+        'part-001.md': 'Lorem ipsum...',
+        'part-002.md': 'Lorem ipsum...'
+      }
+    });
+
+    const folder = `${process.cwd()}/mock-project/`;
+    const steps = getExistingStepNums(folder);
+    const expected = [1, 2];
+
+    expect(steps).toEqual(expected);
+  });
+
+  it('should ignore text formatting and files named final.md', () => {
+    mock({
+      'mock-project': {
+        'final.md': 'Lorem ipsum...',
+        'part-001.md': 'Lorem ipsum...'
+      }
+    });
+
+    const folder = `${process.cwd()}/mock-project/`;
+    const steps = getExistingStepNums(folder);
+    const expected = [1];
+
+    expect(steps).toEqual(expected);
+  });
+
+  it('should throw if file names do not follow naming convention', () => {
+    mock({
+      'mock-project': {
+        'part-001.md': 'Lorem ipsum...',
+        'part-002.md': 'Lorem ipsum...',
+        'part002.md': 'Lorem ipsum...'
+      }
+    });
+
+    const folder = `${process.cwd()}/mock-project/`;
+
+    expect(() => {
+      getExistingStepNums(folder);
+    }).toThrow();
+  });
+
+  it('should return empty array if there are no markdown files', () => {
+    mock({
+      'mock-project': {
+        'part-001.js': 'Lorem ipsum...',
+        'part-002.css': 'Lorem ipsum...'
+      }
+    });
+
+    const folder = `${process.cwd()}/mock-project/`;
+    const steps = getExistingStepNums(folder);
+    const expected = [];
+
+    expect(steps).toEqual(expected);
+  });
+
+  afterAll(() => {
+    mock.restore();
+  });
+});