feat(dom): DOM - toHaveDescription

packages/dom/src/lib/ElementAssertion.ts

@@ -1,7 +1,7 @@
 import { Assertion, AssertionError } from "@assertive-ts/core";
 import equal from "fast-deep-equal";
 
-import { getExpectedAndReceivedStyles } from "./helpers/helpers";
+import { getExpectedAndReceivedStyles, getAccessibleDescription } from "./helpers/helpers";
 
 export class ElementAssertion<T extends Element> extends Assertion<T> {
 
@@ -260,6 +260,71 @@ export class ElementAssertion<T extends Element> extends Assertion<T> {
     });
   }
 
+  /**
+   * Asserts that the element has an accessible description.
+   *
+   * The accessible description is computed from the `aria-describedby`
+   * attribute, which references one or more elements by ID. The text
+   * content of those elements is combined to form the description.
+   *
+   * @example
+   * ```
+   * // Check if element has any description
+   * expect(element).toHaveDescription();
+   *
+   * // Check if element has specific description text
+   * expect(element).toHaveDescription('Expected description text');
+   *
+   * // Check if element description matches a regex pattern
+   * expect(element).toHaveDescription(/description pattern/i);
+   * ```
+   *
+   * @param expectedDescription
+   * - Optional expected description (string or RegExp).
+   * @returns the assertion instance.
+   */
+
+  public toHaveDescription(expectedDescription?: string | RegExp): this {
+    const description = getAccessibleDescription(this.actual);
+    const hasExpectedValue = expectedDescription !== undefined;
+
+    const matchesExpectation = (desc: string): boolean => {
+      if (!hasExpectedValue) {
+        return Boolean(desc);
+      }
+      return expectedDescription instanceof RegExp
+        ? expectedDescription.test(desc)
+        : desc === expectedDescription;
+    };
+
+    const formatExpectation = (isRegExp: boolean): string =>
+      isRegExp ? `matching ${expectedDescription}` : `"${expectedDescription}"`;
+
+    const error = new AssertionError({
+      actual: description,
+      expected: expectedDescription,
+      message: hasExpectedValue
+        ? `Expected the element to have description ${formatExpectation(expectedDescription instanceof RegExp)}, ` +
+        `but received "${description}"`
+        : "Expected the element to have a description",
+    });
+
+    const invertedError = new AssertionError({
+      actual: description,
+      expected: expectedDescription,
+      message: hasExpectedValue
+        ? `Expected the element NOT to have description ${formatExpectation(expectedDescription instanceof RegExp)}, ` +
+        `but received "${description}"`
+        : `Expected the element NOT to have a description, but received "${description}"`,
+    });
+
+    return this.execute({
+      assertWhen: matchesExpectation(description),
+      error,
+      invertedError,
+    });
+  }
+
   /**
    * Helper method to assert the presence or absence of class names.
    *

packages/dom/src/lib/helpers/helpers.ts

@@ -73,3 +73,42 @@ export const getExpectedAndReceivedStyles =
       elementProcessedStyle,
     ];
 };
+
+/**
+ * Normalizes text by collapsing whitespace and trimming.
+ *
+ * @param text - The text to normalize.
+ * @returns The normalized text.
+ */
+export function normalizeText(text: string): string {
+  return text.replace(/\s+/g, " ").trim();
+}
+
+/**
+ * Gets the accessible description of an element based on aria-describedby.
+ *
+ * @param actual - The element to get the description from.
+ * @returns The normalized description text.
+ */
+export function getAccessibleDescription(actual: Element): string {
+  const ariaDescribedBy = actual.getAttribute("aria-describedby") || "";
+  const descriptionIDs = ariaDescribedBy
+    .split(/\s+/)
+    .filter(Boolean);
+
+  if (descriptionIDs.length === 0) {
+    return "";
+  }
+
+  const getElementText = (id: string): string | null => {
+    const element = actual.ownerDocument.getElementById(id);
+    return element?.textContent || null;
+  };
+
+  return normalizeText(
+    descriptionIDs
+      .map(getElementText)
+      .filter((text): text is string => text !== null)
+      .join(" "),
+  );
+}

packages/dom/test/unit/lib/ElementAssertion.test.tsx

@@ -3,6 +3,7 @@ import { render } from "@testing-library/react";
 
 import { ElementAssertion } from "../../../src/lib/ElementAssertion";
 
+import { DescriptionTestComponent } from "./fixtures/descriptionTestComponent";
 import { FocusTestComponent } from "./fixtures/focusTestComponent";
 import { HaveClassTestComponent } from "./fixtures/haveClassTestComponent";
 import { NestedElementsTestComponent } from "./fixtures/nestedElementsTestComponent";
@@ -411,4 +412,124 @@ describe("[Unit] ElementAssertion.test.ts", () => {
       });
     });
   });
+
+  describe(".toHaveDescription", () => {
+    context("when checking for any description", () => {
+      context("when the element has a description", () => {
+        it("returns the assertion instance", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-single");
+          const test = new ElementAssertion(button);
+
+          expect(test.toHaveDescription()).toBeEqual(test);
+
+          expect(() => test.not.toHaveDescription())
+            .toThrowError(AssertionError)
+            .toHaveMessage('Expected the element NOT to have a description, but received "This is a description"');
+        });
+      });
+
+      context("when the element does not have a description", () => {
+        it("throws an assertion error", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-no-description");
+          const test = new ElementAssertion(button);
+
+          expect(() => test.toHaveDescription())
+            .toThrowError(AssertionError)
+            .toHaveMessage("Expected the element to have a description");
+
+          expect(test.not.toHaveDescription()).toBeEqual(test);
+        });
+      });
+    });
+
+    context("when checking for specific description text", () => {
+      context("when the element has the expected description", () => {
+        it("returns the assertion instance", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-single");
+          const test = new ElementAssertion(button);
+
+          expect(test.toHaveDescription("This is a description")).toBeEqual(test);
+
+          expect(() => test.not.toHaveDescription("This is a description"))
+            .toThrowError(AssertionError)
+            .toHaveMessage(
+              'Expected the element NOT to have description "This is a description", ' +
+              'but received "This is a description"',
+            );
+        });
+      });
+
+      context("when the element has multiple descriptions combined", () => {
+        it("returns the assertion instance", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-multiple");
+          const test = new ElementAssertion(button);
+
+          expect(test.toHaveDescription("This is a description Additional info")).toBeEqual(test);
+
+          expect(() => test.not.toHaveDescription("This is a description Additional info"))
+            .toThrowError(AssertionError)
+            .toHaveMessage(
+              'Expected the element NOT to have description "This is a description Additional info", ' +
+              'but received "This is a description Additional info"',
+            );
+        });
+      });
+
+      context("when the element does not have the expected description", () => {
+        it("throws an assertion error", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-single");
+          const test = new ElementAssertion(button);
+
+          expect(() => test.toHaveDescription("Wrong description"))
+            .toThrowError(AssertionError)
+            .toHaveMessage(
+              'Expected the element to have description "Wrong description", but received "This is a description"',
+            );
+
+          expect(test.not.toHaveDescription("Wrong description")).toBeEqual(test);
+        });
+      });
+    });
+
+    context("when checking with a RegExp pattern", () => {
+      context("when the description matches the pattern", () => {
+        it("returns the assertion instance", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-single");
+          const test = new ElementAssertion(button);
+
+          expect(test.toHaveDescription(/description/i)).toBeEqual(test);
+
+          expect(() => test.not.toHaveDescription(/description/i))
+            .toThrowError(AssertionError)
+            .toHaveMessage(
+              "Expected the element NOT to have description matching /description/i, " +
+              'but received "This is a description"',
+            );
+        });
+      });
+
+      context("when the description does not match the pattern", () => {
+        it("throws an assertion error", () => {
+          const { getByTestId } = render(<DescriptionTestComponent />);
+          const button = getByTestId("button-single");
+          const test = new ElementAssertion(button);
+
+          expect(() => test.toHaveDescription(/wrong pattern/))
+            .toThrowError(AssertionError)
+            .toHaveMessage(
+              "Expected the element to have description matching /wrong pattern/, " +
+              'but received "This is a description"',
+            );
+
+          expect(test.not.toHaveDescription(/wrong pattern/)).toBeEqual(test);
+        });
+      });
+    });
+  });
 });

packages/dom/test/unit/lib/fixtures/descriptionTestComponent.tsx

@@ -0,0 +1,29 @@
+import { ReactElement } from "react";
+
+export function DescriptionTestComponent(): ReactElement {
+  return (
+    <div>
+      <div id="description-1">{"This is a description"}</div>
+      <div id="description-2">{"Additional info"}</div>
+      <div id="description-3">{"More details here"}</div>
+
+      <button aria-describedby="description-1" data-testid="button-single">
+        {"Button with single description"}
+      </button>
+
+      <button aria-describedby="description-1 description-2" data-testid="button-multiple">
+        {"Button with multiple descriptions"}
+      </button>
+
+      <button data-testid="button-no-description">
+        {"Button without description"}
+      </button>
+
+      <input
+        type="text"
+        aria-describedby="description-3"
+        data-testid="input-with-description"
+      />
+    </div>
+  );
+}