test: cover conversation context edge cases

tests/moderation/conversationContext.test.ts

@@ -59,4 +59,88 @@ describe("buildConversationPromptMessages", () => {
     expect(lines.some((line) => line.includes("edited"))).toBe(true);
     expect(lines.some((line) => line.includes("original"))).toBe(false);
   });
+
+  it("empty targets returns only fitting context or empty string if no context", () => {
+    // Case 1: No context, no targets
+    const lines1 = buildConversationPromptMessages({
+      contextBefore: [],
+      targets: [],
+      maxTokens: 1000,
+    });
+    expect(lines1).toEqual([]);
+
+    // Case 2: Context but no targets
+    const lines2 = buildConversationPromptMessages({
+      contextBefore: [message("a", "hello", 1)],
+      targets: [],
+      maxTokens: 1000,
+    });
+    expect(lines2).toHaveLength(1);
+    expect(lines2[0]).toContain("[context]");
+  });
+
+  it("maxTokens budget includes target lines even when targets exceed budget", () => {
+    // Create targets that exceed budget
+    const longContent = "x".repeat(500); // ~125 tokens
+    const targets = [
+      message("t1", longContent, 1),
+      message("t2", longContent, 2),
+      message("t3", longContent, 3),
+    ];
+
+    const lines = buildConversationPromptMessages({
+      contextBefore: [message("c1", "context", 0)],
+      targets,
+      maxTokens: 200, // Only 200 tokens, but targets alone are ~375
+    });
+
+    // All targets should be included
+    expect(lines.some((line) => line.includes("id=t1"))).toBe(true);
+    expect(lines.some((line) => line.includes("id=t2"))).toBe(true);
+    expect(lines.some((line) => line.includes("id=t3"))).toBe(true);
+
+    // Context should be excluded due to budget
+    expect(lines.some((line) => line.includes("id=c1"))).toBe(false);
+  });
+
+  it("most recent context is kept when context budget is tight", () => {
+    // Create multiple context messages with different timestamps
+    // Use longer content to ensure they consume meaningful tokens
+    const contextBefore = [
+      message(
+        "c1",
+        "oldest context with some extra words to make it longer",
+        1000,
+      ),
+      message(
+        "c2",
+        "middle context with some extra words to make it longer",
+        2000,
+      ),
+      message(
+        "c3",
+        "newest context with some extra words to make it longer",
+        3000,
+      ),
+    ];
+
+    const lines = buildConversationPromptMessages({
+      contextBefore,
+      targets: [message("t1", "target message", 4000)],
+      maxTokens: 90, // Very tight budget: target ~35 tokens, room for ~55 tokens of context (fits only c3)
+    });
+
+    // Should include target
+    expect(lines.some((line) => line.includes("id=t1"))).toBe(true);
+
+    // Should include newest context (c3) but not oldest (c1)
+    // With tight budget, only the most recent context should fit
+    expect(lines.some((line) => line.includes("id=c3"))).toBe(true);
+    expect(lines.some((line) => line.includes("id=c1"))).toBe(false);
+
+    // Verify chronological order is maintained
+    const indexT1 = lines.findIndex((line) => line.includes("id=t1"));
+    const indexC3 = lines.findIndex((line) => line.includes("id=c3"));
+    expect(indexC3).toBeLessThan(indexT1); // context before target
+  });
 });