test: cover tool metadata diffs

src/__tests__/diff.test.ts

@@ -0,0 +1,62 @@
+import { compareProbeResults } from "../diff.js";
+import type { ProbeResult } from "../types.js";
+
+function createProbeResult(toolDescription: string, argumentDescription: string): ProbeResult {
+  return {
+    initialize: {
+      serverInfo: {
+        name: "test-server",
+        version: "1.0.0",
+      },
+      capabilities: {
+        tools: {},
+      },
+    },
+    instructions: null,
+    tools: {
+      tools: [
+        {
+          name: "greet",
+          description: toolDescription,
+          inputSchema: {
+            type: "object",
+            properties: {
+              name: {
+                type: "string",
+                description: argumentDescription,
+              },
+            },
+            required: ["name"],
+          },
+        },
+      ],
+    },
+    prompts: null,
+    resources: null,
+    resourceTemplates: null,
+    customResponses: new Map(),
+  };
+}
+
+describe("compareProbeResults", () => {
+  it("reports tool description and schema description changes as tools endpoint diffs", () => {
+    const baseResult = createProbeResult("Greet a user by name", "Name of the user to greet");
+    const targetResult = createProbeResult(
+      "Greet a user by full name",
+      "Full display name of the user to greet"
+    );
+
+    const diffs = compareProbeResults(baseResult, targetResult);
+
+    expect(diffs).toHaveLength(1);
+    expect(diffs[0].endpoint).toBe("tools");
+    expect(diffs[0].diff).toContain('tools[greet].description: "Greet a user by name"');
+    expect(diffs[0].diff).toContain('tools[greet].description: "Greet a user by full name"');
+    expect(diffs[0].diff).toContain(
+      'tools[greet].inputSchema.properties.name.description: "Name of the user to greet"'
+    );
+    expect(diffs[0].diff).toContain(
+      'tools[greet].inputSchema.properties.name.description: "Full display name of the user to greet"'
+    );
+  });
+});