test: tighten shared singleton and sample coverage

src/shared/string-sample.test.ts

@@ -4,6 +4,7 @@ import { summarizeStringEntries } from "./string-sample.js";
 describe("summarizeStringEntries", () => {
   it("returns emptyText for empty lists", () => {
     expect(summarizeStringEntries({ entries: [], emptyText: "any" })).toBe("any");
+    expect(summarizeStringEntries({ entries: null })).toBe("");
   });
 
   it("joins short lists without a suffix", () => {
@@ -18,4 +19,27 @@ describe("summarizeStringEntries", () => {
       }),
     ).toBe("a, b, c, d (+1)");
   });
+
+  it("uses a floored limit and clamps non-positive values to one entry", () => {
+    expect(
+      summarizeStringEntries({
+        entries: ["a", "b", "c"],
+        limit: 2.8,
+      }),
+    ).toBe("a, b (+1)");
+    expect(
+      summarizeStringEntries({
+        entries: ["a", "b", "c"],
+        limit: 0,
+      }),
+    ).toBe("a (+2)");
+  });
+
+  it("uses the default limit when none is provided", () => {
+    expect(
+      summarizeStringEntries({
+        entries: ["a", "b", "c", "d", "e", "f", "g"],
+      }),
+    ).toBe("a, b, c, d, e, f (+1)");
+  });
 });