diff --git a/packages/core-components/src/components/LogViewer/LogLine.test.tsx b/packages/core-components/src/components/LogViewer/LogLine.test.tsx
new file mode 100644
index 0000000000..2b4513221a
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+++ b/packages/core-components/src/components/LogViewer/LogLine.test.tsx
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed 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 { ChunkModifiers } from './AnsiProcessor';
+import { getModifierClasses } from './LogLine';
+
+describe('getModifierClasses', () => {
+  const classes = {
+    modifierBold: 'bold',
+    modifierItalic: 'italic',
+    modifierUnderline: 'underline',
+    modifierForegroundBlack: 'black',
+    modifierForegroundRed: 'red',
+    modifierForegroundGreen: 'green',
+    modifierForegroundYellow: 'yellow',
+    modifierForegroundBlue: 'blue',
+    modifierForegroundMagenta: 'magenta',
+    modifierForegroundCyan: 'cyan',
+    modifierForegroundWhite: 'white',
+    modifierForegroundGrey: 'grey',
+    modifierBackgroundBlack: 'bg-black',
+    modifierBackgroundRed: 'bg-red',
+    modifierBackgroundGreen: 'bg-green',
+    modifierBackgroundYellow: 'bg-yellow',
+    modifierBackgroundBlue: 'bg-blue',
+    modifierBackgroundMagenta: 'bg-magenta',
+    modifierBackgroundCyan: 'bg-cyan',
+    modifierBackgroundWhite: 'bg-white',
+    modifierBackgroundGrey: 'bg-grey',
+  };
+  const curried = (modifiers: ChunkModifiers) =>
+    getModifierClasses(
+      classes as Parameters<typeof getModifierClasses>[0],
+      modifiers,
+    );
+
+  it('should transform modifiers to classes', () => {
+    expect(curried({})).toEqual(undefined);
+    expect(curried({ bold: true })).toEqual('bold');
+    expect(curried({ italic: true })).toEqual('italic');
+    expect(curried({ underline: true })).toEqual('underline');
+    expect(curried({ foreground: 'black' })).toEqual('black');
+    expect(curried({ background: 'black' })).toEqual('bg-black');
+    expect(
+      curried({
+        bold: true,
+        italic: true,
+        underline: true,
+        foreground: 'red',
+        background: 'red',
+      }),
+    ).toEqual('bold italic underline red bg-red');
+  });
+});