feat(native): add toHaveStyle (#152)

Author: ACR1209

packages/native/src/lib/ElementAssertion.ts

@@ -2,7 +2,14 @@ import { Assertion, AssertionError } from "@assertive-ts/core";
 import { get } from "dot-prop-immutable";
 import { ReactTestInstance } from "react-test-renderer";
 
-import { instanceToString, isEmpty } from "./helpers/helpers";
+import {
+  instanceToString,
+  isEmpty,
+  getFlattenedStyle,
+  styleToString,
+  textMatches,
+} from "./helpers/helpers";
+import { AssertiveStyle, TestableTextMatcher, TextContent } from "./helpers/types";
 
 export class ElementAssertion extends Assertion<ReactTestInstance> {
   public constructor(actual: ReactTestInstance) {
@@ -200,6 +207,129 @@ export class ElementAssertion extends Assertion<ReactTestInstance> {
     });
   }
 
+  /**
+   * Asserts that a component has the specified style(s) applied.
+   *
+   * This method supports both single style objects and arrays of style objects.
+   * It checks if all specified style properties match on the target element.
+   *
+   * @example
+   * ```
+   * expect(element).toHaveStyle({ backgroundColor: "red" });
+   * expect(element).toHaveStyle([{ backgroundColor: "red" }]);
+   * ```
+   *
+   * @param style - A style object to check for.
+   * @returns the assertion instance
+   */
+  public toHaveStyle(style: AssertiveStyle): this {
+    const stylesOnElement: AssertiveStyle = get(this.actual, "props.style", {});
+
+    const flattenedElementStyle = getFlattenedStyle(stylesOnElement);
+    const flattenedStyle = getFlattenedStyle(style);
+
+    const hasStyle = Object.keys(flattenedStyle)
+      .every(key => flattenedElementStyle[key] === flattenedStyle[key]);
+
+    const error = new AssertionError({
+      actual: this.actual,
+      message: `Expected element ${this.toString()} to have style: \n${styleToString(flattenedStyle)}`,
+    });
+
+    const invertedError = new AssertionError({
+      actual: this.actual,
+      message: `Expected element ${this.toString()} NOT to have style: \n${styleToString(flattenedStyle)}`,
+    });
+
+    return this.execute({
+      assertWhen: hasStyle,
+      error,
+      invertedError,
+    });
+  }
+
+  /**
+   * Check if the element has text content matching the provided string,
+   * RegExp, or function.
+   *
+   * @example
+   * ```
+   * expect(element).toHaveTextContent("Hello World");
+   * expect(element).toHaveTextContent(/Hello/);
+   * expect(element).toHaveTextContent(text => text.startsWith("Hello"));
+   * ```
+   *
+   * @param text - The text to check for.
+   * @returns the assertion instance
+   */
+  public toHaveTextContent(text: TestableTextMatcher): this {
+    const actualTextContent = this.getTextContent(this.actual);
+    const matchesText = textMatches(actualTextContent, text);
+
+    const error = new AssertionError({
+      actual: this.actual,
+      message: `Expected element ${this.toString()} to have text content matching '` +
+        `${text.toString()}'.`,
+    });
+
+    const invertedError = new AssertionError({
+      actual: this.actual,
+      message:
+        `Expected element ${this.toString()} NOT to have text content matching '` +
+        `${text.toString()}'.`,
+    });
+
+    return this.execute({
+      assertWhen: matchesText,
+      error,
+      invertedError,
+    });
+  }
+
+  private getTextContent(element: ReactTestInstance): string {
+    if (!element) {
+      return "";
+    }
+
+    if (typeof element === "string") {
+      return element;
+    }
+
+    if (typeof element.props?.value === "string") {
+      return element.props.value;
+    }
+
+    return this.collectText(element).join(" ");
+  }
+
+  private collectText = (element: TextContent): string[] => {
+    if (typeof element === "string") {
+      return [element];
+    }
+
+    if (Array.isArray(element)) {
+      return element.flatMap(child => this.collectText(child));
+    }
+
+    if (element && (typeof element === "object" && "props" in element)) {
+      const value = element.props?.value as TextContent;
+      if (typeof value === "string") {
+        return [value];
+      }
+
+      const children = (element.props?.children as ReactTestInstance[]) ?? element.children;
+      if (!children) {
+        return [];
+      }
+
+      return Array.isArray(children)
+        ? children.flatMap(this.collectText)
+        : this.collectText(children);
+    }
+
+    return [];
+  };
+
   private isElementDisabled(element: ReactTestInstance): boolean {
     const { type } = element;
     const elementType = type.toString();
@@ -208,10 +338,10 @@ export class ElementAssertion extends Assertion<ReactTestInstance> {
     }
 
     return (
-        get(element, "props.aria-disabled")
-        || get(element, "props.disabled", false)
-        || get(element, "props.accessibilityState.disabled", false)
-        || get<ReactTestInstance, string[]>(element, "props.accessibilityStates", []).includes("disabled")
+      get(element, "props.aria-disabled")
+      || get(element, "props.disabled", false)
+      || get(element, "props.accessibilityState.disabled", false)
+      || get<ReactTestInstance, string[]>(element, "props.accessibilityStates", []).includes("disabled")
     );
   }
 

packages/native/src/lib/helpers/helpers.ts

@@ -1,5 +1,8 @@
+import { StyleSheet } from "react-native";
 import { ReactTestInstance } from "react-test-renderer";
 
+import { AssertiveStyle, StyleObject, TestableTextMatcher } from "./types";
+
 /**
  * Checks if a value is empty.
  *
@@ -31,3 +34,49 @@ export function instanceToString(instance: ReactTestInstance | null): string {
 
   return `<${instance.type.toString()} ... />`;
 }
+
+/**
+ * Checks if a text matches a given matcher.
+ *
+ * @param text - The text to check.
+ * @param matcher - The matcher to use for comparison.
+ * @returns `true` if the text matches the matcher, `false` otherwise.
+ * @throws Error if the matcher is not a string, RegExp, or function.
+ * @example
+ * ```ts
+ * textMatches("Hello World", "Hello World"); // true
+ * textMatches("Hello World", /Hello/); // true
+ * textMatches("Hello World", (text) => text.startsWith("Hello")); // true
+ * textMatches("Hello World", "Goodbye"); // false
+ * textMatches("Hello World", /Goodbye/); // false
+ * textMatches("Hello World", (text) => text.startsWith("Goodbye")); // false
+ * ```
+ */
+export function textMatches(
+  text: string,
+  matcher: TestableTextMatcher,
+): boolean {
+  if (typeof matcher === "string") {
+    return text.includes(matcher);
+  }
+
+  if (matcher instanceof RegExp) {
+    return matcher.test(text);
+  }
+
+  if (typeof matcher === "function") {
+    return matcher(text);
+  }
+
+  throw new Error("Matcher must be a string, RegExp, or function.");
+}
+
+export function getFlattenedStyle(style: AssertiveStyle): StyleObject {
+    const flattenedStyle = StyleSheet.flatten(style);
+    return flattenedStyle ? (flattenedStyle as StyleObject) : {};
+}
+
+export function styleToString(flattenedStyle: StyleObject): string {
+  const styleEntries = Object.entries(flattenedStyle);
+  return styleEntries.map(([key, value]) => `\t- ${key}: ${String(value)};`).join("\n");
+}

packages/native/src/lib/helpers/types.ts

@@ -0,0 +1,34 @@
+import { ImageStyle, StyleProp, TextStyle, ViewStyle } from "react-native";
+import { ReactTestInstance } from "react-test-renderer";
+
+/**
+ * Type representing a style that can be applied to a React Native component.
+ * It can be a style for text, view, or image components.
+ */
+export type Style = TextStyle | ViewStyle | ImageStyle;
+
+/**
+ * Type for a style prop that can be applied to a React Native component.
+ * It can be a single style or an array of styles.
+ */
+export type AssertiveStyle = StyleProp<Style>;
+
+/**
+ * Type representing a style object when flattened.
+ * It is a record where the keys are strings and the values can be of any type.
+ */
+export type StyleObject = Record<string, unknown>;
+
+/**
+ * Type representing a matcher for text in tests.
+ *
+ * It can be a string, a regular expression, or a function that
+ * takes a string and returns a boolean.
+ */
+export type TestableTextMatcher = string | RegExp | ((text: string) => boolean);
+
+/**
+ * Type representing a value that can be used to match text content in tests.
+ * It can be a string, a ReactTestInstance, or an array of ReactTestInstances.
+ */
+export type TextContent = string | ReactTestInstance | ReactTestInstance[];