diff --git a/test/border-background.test.ts b/test/border-background.test.ts
new file mode 100644
index 0000000..dbc6785
--- /dev/null
+++ b/test/border-background.test.ts
@@ -0,0 +1,64 @@
+import { beforeEach, describe, expect, it } from "./suite.ts";
+import { createTerm, type Term } from "../term.ts";
+import { close, fixed, open, rgba, text } from "../ops.ts";
+
+const decode = (b: Uint8Array) => new TextDecoder().decode(b);
+
+describe("border background color", () => {
+  let term: Term;
+
+  beforeEach(async () => {
+    term = await createTerm({ width: 12, height: 4 });
+  });
+
+  it("emits a uniform bg SGR on border cells", () => {
+    let ansi = decode(
+      term.render([
+        open("box", {
+          layout: { width: fixed(8), height: fixed(3), direction: "ttb" },
+          border: {
+            color: rgba(255, 255, 255),
+            bg: rgba(0, 0, 255), // proposed: blue border background
+            left: 1,
+            right: 1,
+            top: 1,
+            bottom: 1,
+            // deno-lint-ignore no-explicit-any
+          } as any,
+        }),
+        text("Hi"),
+        close(),
+      ]).output,
+    );
+
+    // pins down: border cells carry a blue background SGR
+    expect(ansi).toContain("\x1b[48;2;0;0;255");
+  });
+
+  it("emits the border fg AND bg together on a corner cell", () => {
+    let ansi = decode(
+      term.render([
+        open("box", {
+          layout: { width: fixed(8), height: fixed(3), direction: "ttb" },
+          border: {
+            color: rgba(255, 0, 0), // red fg
+            bg: rgba(0, 0, 255), // blue bg
+            left: 1,
+            right: 1,
+            top: 1,
+            bottom: 1,
+            // deno-lint-ignore no-explicit-any
+          } as any,
+        }),
+        text("Hi"),
+        close(),
+      ]).output,
+    );
+
+    let before = ansi.slice(0, ansi.indexOf("┌"));
+    // pins down: red fg active on the run leading to the top-left corner
+    expect(before).toContain("\x1b[38;2;255;0;0");
+    // pins down: blue bg active on the same corner cell
+    expect(before).toContain("\x1b[48;2;0;0;255");
+  });
+});