diff --git a/lib/shared/markdown.test.js b/lib/shared/markdown.test.js
new file mode 100644
--- /dev/null
+++ b/lib/shared/markdown.test.js
@@ -0,0 +1,54 @@
+// @flow
+
+import { spoilerRegex } from './markdown.js';
+
+// Each of the below tests is subject to the following RegEx pattern:
+// Spoiler RegEx: /^\|\|([^\n]+?)\|\|/g
+
+describe('spoilerRegex', () => {
+  it('We expect a spoiler with a single space character to match.', () => {
+    expect('|| ||').toMatch(spoilerRegex);
+  });
+
+  it('We expect a spoiler with regular text + spaces to match (1).', () => {
+    expect('|| hello ||').toMatch(spoilerRegex);
+  });
+
+  it('We expect a spoiler with regular text + spaces to match (2).', () => {
+    expect('||SPOILER||').toMatch(spoilerRegex);
+  });
+
+  it('We expect a spoiler containing any number of || within it to match (1).', () => {
+    expect('|| || ||').toMatch(spoilerRegex);
+  });
+
+  it('We expect a spoiler containing any number of || within it to match (2).', () => {
+    expect('||||||').toMatch(spoilerRegex);
+  });
+
+  it('We expect a spoiler containing any number of || within it, as well as regular text + spaces, to match.', () => {
+    expect('||SPOILER||SPOILER||').toMatch(spoilerRegex);
+  });
+
+  it('We do not expect a spoiler containing a new line character to match (1).', () => {
+    expect('||\n||').not.toMatch(spoilerRegex);
+  });
+
+  it('We do not expect a spoiler containing a new line character to match (2).', () => {
+    expect('||\r\n||').not.toMatch(spoilerRegex);
+  });
+
+  it('We do not expect an empty spoiler to match.', () => {
+    expect('||||').not.toMatch(spoilerRegex);
+  });
+
+  it('We expect a spoiler containing a single space to match, even when split across multiple lines.', () => {
+    expect('|| \
+    ||').toMatch(spoilerRegex);
+  });
+
+  it('We do not expect a spoiler containing a new line character to match (3).', () => {
+    expect('|| \n\
+    ||').not.toMatch(spoilerRegex);
+  });
+});