add test for encrypted private key

test/signature-unit-tests.spec.ts

@@ -1265,4 +1265,14 @@ describe("Signature unit tests", function () {
       "MIIDZ",
     );
   });
+
+  it("can decrypt the private key when privateKeyPass is set", function () {
+    const xml = "<root><x /></root>";
+    const sig = new SignedXml();
+    sig.privateKey = fs.readFileSync("./test/static/client_encrypted.pem");
+    sig.privateKeyPass = "password";
+    sig.canonicalizationAlgorithm = "http://www.w3.org/2001/10/xml-exc-c14n#";
+    sig.signatureAlgorithm = "http://www.w3.org/2000/09/xmldsig#rsa-sha1";
+    expect(() => sig.computeSignature(xml)).to.not.throw();
+  });
 });