1 files changed, 39 insertions, 0 deletions
diff --git a/src/lib/__tests__/charts.test.ts b/src/lib/__tests__/charts.test.ts
new file mode 100644
index 0000000..e81be16
--- /dev/null
+++ b/src/lib/__tests__/charts.test.ts
@@ -0,0 +1,39 @@
+import { renderNumberLabels } from '../charts';
+
+// test for renderNumberLabels
+
+describe('renderNumberLabels', () => {
+  test.each([
+    ['1000000', '1.0m'],
+    ['2500000', '2.5m'],
+  ])("formats numbers ≥ 1 million as 'Xm' (%s → %s)", (input, expected) => {
+    expect(renderNumberLabels(input)).toBe(expected);
+  });
+
+  test.each([['150000', '150k']])("formats numbers ≥ 100K as 'Xk' (%s → %s)", (input, expected) => {
+    expect(renderNumberLabels(input)).toBe(expected);
+  });
+
+  test.each([
+    ['12500', '12.5k'],
+  ])("formats numbers ≥ 10K as 'X.Xk' (%s → %s)", (input, expected) => {
+    expect(renderNumberLabels(input)).toBe(expected);
+  });
+
+  test.each([['1500', '1.50k']])("formats numbers ≥ 1K as 'X.XXk' (%s → %s)", (input, expected) => {
+    expect(renderNumberLabels(input)).toBe(expected);
+  });
+
+  test.each([
+    ['999', '999'],
+  ])('calls formatNumber for values < 1000 (%s → %s)', (input, expected) => {
+    expect(renderNumberLabels(input)).toBe(expected);
+  });
+
+  test.each([
+    ['0', '0'],
+    ['-5000', '-5000'],
+  ])('handles edge cases correctly (%s → %s)', (input, expected) => {
+    expect(renderNumberLabels(input)).toBe(expected);
+  });
+});