test: unit tests for splitStyles

src/utils/__tests__/splitStyles.test.ts

@@ -0,0 +1,84 @@
+import type { ViewStyle } from 'react-native';
+
+import { splitStyles } from '../splitStyles';
+
+describe('splitStyles', () => {
+  const styles: Readonly<ViewStyle> = Object.freeze({
+    backgroundColor: 'red',
+    marginTop: 1,
+    marginBottom: 2,
+    marginLeft: 3,
+    padding: 4,
+    borderTopLeftRadius: 5,
+    borderTopRightRadius: 6,
+    right: 4,
+  });
+
+  it('splits margins, paddings, and border radiuses correctly', () => {
+    const marginPredicate = (style: string) => style.startsWith('margin');
+    const paddingPredicate = (style: string) => style.startsWith('padding');
+    const borderRadiusPredicate = (style: string) =>
+      style.startsWith('border') && style.endsWith('Radius');
+    const [filteredStyles, marginStyles, paddingStyles, borderRadiusStyles] =
+      splitStyles(
+        styles,
+        marginPredicate,
+        paddingPredicate,
+        borderRadiusPredicate
+      );
+
+    expect(keysLength(filteredStyles)).toBeGreaterThan(0);
+    expect(keysLength(filteredStyles)).toBeLessThan(keysLength(styles));
+    for (const style in filteredStyles) {
+      expect(marginPredicate(style)).toBeFalsy();
+      expect(paddingPredicate(style)).toBeFalsy();
+      expect(borderRadiusPredicate(style)).toBeFalsy();
+    }
+
+    expect(keysLength(marginStyles)).toBeGreaterThan(0);
+    for (const style in marginStyles) {
+      expect(marginPredicate(style)).toBeTruthy();
+    }
+
+    expect(keysLength(paddingStyles)).toBeGreaterThan(0);
+    for (const style in paddingStyles) {
+      expect(paddingPredicate(style)).toBeTruthy();
+    }
+
+    expect(keysLength(borderRadiusStyles)).toBeGreaterThan(0);
+    for (const style in borderRadiusStyles) {
+      expect(borderRadiusPredicate(style)).toBeTruthy();
+    }
+  });
+
+  it('filtered styles is an empty object if all styles matched some predicate', () => {
+    const styles = {
+      margin: 5,
+      padding: 6,
+    };
+    const [filteredStyles] = splitStyles(
+      styles,
+      (style) => style.startsWith('margin'),
+      (style) => style.startsWith('padding')
+    );
+
+    expect(keysLength(filteredStyles)).toBe(0);
+  });
+
+  it('processes predicates in order', () => {
+    const [, marginStyles, marginStyles2, marginStyles3] = splitStyles(
+      styles,
+      (style) => style.startsWith('margin'),
+      (style) => style.startsWith('margin'),
+      (style) => style.startsWith('margin')
+    );
+
+    expect(keysLength(marginStyles)).toBeGreaterThan(0);
+    expect(keysLength(marginStyles2)).toBe(0);
+    expect(keysLength(marginStyles3)).toBe(0);
+  });
+});
+
+function keysLength(object: object): number {
+  return Object.keys(object).length;
+}