diff --git a/src/plugins/config-state.test.ts b/src/plugins/config-state.test.ts
new file mode 100644
index 000000000..c5c4924eb
--- /dev/null
+++ b/src/plugins/config-state.test.ts
@@ -0,0 +1,52 @@
+import { describe, expect, it } from "vitest";
+
+import { normalizePluginsConfig } from "./config-state.js";
+
+describe("normalizePluginsConfig", () => {
+  it("uses default memory slot when not specified", () => {
+    const result = normalizePluginsConfig({});
+    expect(result.slots.memory).toBe("memory-core");
+  });
+
+  it("respects explicit memory slot value", () => {
+    const result = normalizePluginsConfig({
+      slots: { memory: "custom-memory" },
+    });
+    expect(result.slots.memory).toBe("custom-memory");
+  });
+
+  it("disables memory slot when set to 'none'", () => {
+    const result = normalizePluginsConfig({
+      slots: { memory: "none" },
+    });
+    expect(result.slots.memory).toBeNull();
+  });
+
+  it("disables memory slot when set to 'None' (case insensitive)", () => {
+    const result = normalizePluginsConfig({
+      slots: { memory: "None" },
+    });
+    expect(result.slots.memory).toBeNull();
+  });
+
+  it("trims whitespace from memory slot value", () => {
+    const result = normalizePluginsConfig({
+      slots: { memory: "  custom-memory  " },
+    });
+    expect(result.slots.memory).toBe("custom-memory");
+  });
+
+  it("uses default when memory slot is empty string", () => {
+    const result = normalizePluginsConfig({
+      slots: { memory: "" },
+    });
+    expect(result.slots.memory).toBe("memory-core");
+  });
+
+  it("uses default when memory slot is whitespace only", () => {
+    const result = normalizePluginsConfig({
+      slots: { memory: "   " },
+    });
+    expect(result.slots.memory).toBe("memory-core");
+  });
+});