Add unit tests for getNewIndexFromPresets function

packages/edit-site/src/components/global-styles/test/utils.spec.js

@@ -0,0 +1,59 @@
+/**
+ * Internal dependencies
+ */
+import { getNewIndexFromPresets } from '../utils';
+
+const validPresets = {
+	single: [ { slug: 'preset-1' } ],
+	multiple: [ { slug: 'preset-1' }, { slug: 'preset-2' } ],
+	withGaps: [ { slug: 'preset-1' }, { slug: 'preset-3' } ],
+	mixedPrefixes: [
+		{ slug: 'preset-1' },
+		{ slug: 'shadow-2' },
+		{ slug: 'preset-3' },
+	],
+	nonStringSlug: [ { slug: 'preset-1' }, { slug: 2 } ],
+	emptyArray: [],
+};
+
+const invalidPresets = {
+	noMatch: [ { slug: 'preset-alpha' }, { slug: 'preset-beta' } ],
+	emptySlug: [ { slug: '' } ],
+	nullSlug: [ { slug: null } ],
+	undefinedSlug: [ { slug: undefined } ],
+	nonObjectElements: [ 'preset-1' ],
+};
+
+const getExpectedIndex = ( presetKey, presets ) => {
+	if ( presetKey === 'withGaps' ) {
+		return 4;
+	}
+	if ( presetKey === 'mixedPrefixes' ) {
+		return 4;
+	}
+	if ( presetKey === 'nonStringSlug' ) {
+		return 2;
+	}
+	return presets.length + 1;
+};
+
+describe( 'getNewIndexFromPresets', () => {
+	Object.entries( validPresets ).forEach( ( [ presetKey, presets ] ) => {
+		describe( `test valid preset format: ${ presetKey }`, () => {
+			const newIndex = getNewIndexFromPresets( presets, 'preset-' );
+			it( `should return correct new index for ${ presetKey }`, () => {
+				const expectedIndex = getExpectedIndex( presetKey, presets );
+				expect( newIndex ).toBe( expectedIndex );
+			} );
+		} );
+	} );
+
+	Object.entries( invalidPresets ).forEach( ( [ presetKey, presets ] ) => {
+		describe( `test invalid preset format: ${ presetKey }`, () => {
+			const newIndex = getNewIndexFromPresets( presets, 'preset-' );
+			it( `should return 1 for ${ presetKey }`, () => {
+				expect( newIndex ).toBe( 1 );
+			} );
+		} );
+	} );
+} );