fix: 补齐候选诊断环境与证据保护（09-06-release-gate-integrity）

server/tests/unit/routes/reimbursements.amount-guard.test.js

@@ -0,0 +1,31 @@
+const { ensureNonNegativeAmount } = require("../../../src/routes/reimbursements").__testables;
+const { AppError } = require("../../../src/utils/AppError");
+
+describe("reimbursement total amount defense", () => {
+  function assertRejected(value, detail, reasonCode) {
+    let caught;
+    try {
+      ensureNonNegativeAmount(value);
+    } catch (error) {
+      caught = error;
+    }
+    expect(caught).toBeInstanceOf(AppError);
+    expect(caught).toMatchObject({
+      code: "VALID_001",
+      statusCode: 400,
+      details: { total_amount: detail, reasonCode },
+    });
+  }
+
+  it.each([-1, "-0.01", -Number.MIN_VALUE])("directly rejects negative total %s", (value) => {
+    assertRejected(value, "negative_not_allowed", "reimbursement.total_amount_negative_not_allowed");
+  });
+
+  it.each([NaN, Infinity, -Infinity, "not-a-number", undefined])("directly rejects non-finite total %s", (value) => {
+    assertRejected(value, "invalid", "reimbursement.total_amount_invalid");
+  });
+
+  it.each([0, "0.00", 1, "188.80"])("preserves acceptance of finite nonnegative total %s", (value) => {
+    expect(() => ensureNonNegativeAmount(value)).not.toThrow();
+  });
+});