1 files changed, 30 insertions, 0 deletions
diff --git a/spec/frontend/diffs/utils/diff_line_spec.js b/spec/frontend/diffs/utils/diff_line_spec.js
new file mode 100644
index 00000000000..adcb4a4433c
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+++ b/spec/frontend/diffs/utils/diff_line_spec.js
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+import { pickDirection } from '~/diffs/utils/diff_line';
+
+describe('diff_line utilities', () => {
+  describe('pickDirection', () => {
+    const left = {
+      line_code: 'left',
+    };
+    const right = {
+      line_code: 'right',
+    };
+    const defaultLine = {
+      left,
+      right,
+    };
+
+    it.each`
+      code       | pick     | line           | pickDescription
+      ${'left'}  | ${left}  | ${defaultLine} | ${'the left line'}
+      ${'right'} | ${right} | ${defaultLine} | ${'the right line'}
+      ${'junk'}  | ${left}  | ${defaultLine} | ${'the default: the left line'}
+      ${'junk'}  | ${right} | ${{ right }}   | ${"the right line if there's no left line to default to"}
+      ${'right'} | ${left}  | ${{ left }}    | ${"the left line when there isn't a right line to match"}
+    `(
+      'when provided a line and a line code `$code`, picks $pickDescription',
+      ({ code, line, pick }) => {
+        expect(pickDirection({ line, code })).toBe(pick);
+      },
+    );
+  });
+});