diff --git a/src/plugins/expressions/common/expression_functions/specs/tests/theme.test.ts b/src/plugins/expressions/common/expression_functions/specs/tests/theme.test.ts
new file mode 100644
index 0000000000000..93fd64e3a3130
--- /dev/null
+++ b/src/plugins/expressions/common/expression_functions/specs/tests/theme.test.ts
@@ -0,0 +1,64 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { functionWrapper } from './utils';
+import { theme } from '../theme';
+import { ExecutionContext } from '../../../execution/types';
+import { KibanaContext } from '../../../expression_types';
+
+describe('expression_functions', () => {
+  describe('theme', () => {
+    const fn = functionWrapper(theme);
+    let context: ExecutionContext;
+
+    let themeProps;
+
+    beforeEach(() => {
+      themeProps = {
+        font: {
+          family: 'Arial',
+          size: 14,
+        },
+      };
+
+      context = {
+        getInitialInput: () => input,
+        types: {},
+        variables: { theme: themeProps },
+        abortSignal: {} as any,
+        inspectorAdapters: {} as any,
+      };
+    });
+
+    it('returns the selected variable', () => {
+      const actual = fn(null, { variable: 'font.family' }, context);
+      expect(actual).toEqual('Arial');
+    });
+
+    it('returns undefined if variable does not exist', () => {
+      const actual = fn(null, { variable: 'font.weight' }, context);
+      expect(actual).toEqual(undefined);
+    });
+
+    it('returns default if variable does not exist and default is provided', () => {
+      const actual = fn(null, { variable: 'font.weight', default: 'normal' }, context);
+      expect(actual).toEqual('normal');
+    });
+  });
+});