diff --git a/css/test/index.test.js b/css/test/index.test.js
index <HASH>..<HASH> 100644
--- a/css/test/index.test.js
+++ b/css/test/index.test.js
@@ -81,6 +81,12 @@ describe('Draw triangle mixin', () => {
     expect(result.warnings).toHaveLength(0);
     expect(result.css).toMatchSnapshot();
   });
+
+  it('throws error when invalid direction', () => {
+    expect(() => {
+      drawTriangle(null, 'under', '1rem', '#000');
+    }).toThrow();
+  });
 });
 
 describe('Fluid font size mixin', () => {
@@ -121,6 +127,12 @@ describe('Fluid font size mixin', () => {
     expect(result.warnings).toHaveLength(0);
     expect(result.css).toMatchSnapshot();
   });
+
+  it('throws error when invalid size unit', () => {
+    expect(() => {
+      fluidFontSize(null, '16', '32pops', '30em', '100em');
+    }).toThrow('Only px, rem, and em units are supported');
+  });
 });
 
 describe('Make font face mixin', () => {
Add extra tests for CSS mixins for error scenarios