test: add unit tests for buildTransformationString function

Author: manu4543

test/url-generation/buildtransformationString.js

@@ -0,0 +1,26 @@
+const { buildTransformationString } = require("../../src/index");
+const { expect } = require('chai');
+
+describe('buildTransformationString', function () {
+  it('should return an empty string when no transformations are provided', function () {
+    const result = buildTransformationString([{}]);
+    expect(result).to.equal('');
+  });
+
+  it('should generate a transformation string for width only', function () {
+    const result = buildTransformationString([{ width: 300 }]);
+    expect(result).to.equal('w-300');
+  });
+
+  it('should generate a transformation string for multiple transformations', function () {
+    const result = buildTransformationString([
+      {
+        overlay: {
+          type: 'text',
+          text: 'Hello',
+        }
+      }
+    ]);
+    expect(result).to.equal('l-text,i-Hello,l-end');
+  });
+});