Nasal: tests for new operators

- test for nil-member-access
- test for chained nil

test_suite/unit_tests/Scripting/testNasalSys.cxx

@@ -292,3 +292,45 @@ void NasalSysTests::testKeywordArgInHash()
     )");
     CPPUNIT_ASSERT(ok);
 }
+
+void NasalSysTests::testNullAccess()
+{
+    auto nasalSys = globals->get_subsystem<FGNasalSys>();
+    nasalSys->getAndClearErrorList();
+
+    bool ok = FGTestApi::executeNasal(R"(
+        var s =  {
+           bar: 42
+        };
+
+        unitTest.assert_equal(s?.bar, 42);
+
+        var t = nil;
+        var z = t?.bar;
+        unitTest.assert_equal(z, nil);
+        
+
+    )");
+    CPPUNIT_ASSERT(ok);
+    auto errors = nasalSys->getAndClearErrorList();
+    CPPUNIT_ASSERT_EQUAL(errors.size(), static_cast<size_t>(0));
+}
+
+void NasalSysTests::testNullishChain()
+{
+    auto nasalSys = globals->get_subsystem<FGNasalSys>();
+    nasalSys->getAndClearErrorList();
+
+    bool ok = FGTestApi::executeNasal(R"(
+        var t = nil;
+        var s = 'abc';
+
+        unitTest.assert_equal(t ?? 99, 99);
+        unitTest.assert_equal(s ?? 'default', 'abc');
+        unitTest.assert_equal(t ?? 'default', 'default');
+    )");
+
+    CPPUNIT_ASSERT(ok);
+    auto errors = nasalSys->getAndClearErrorList();
+    CPPUNIT_ASSERT_EQUAL(errors.size(), static_cast<size_t>(0));
+}

test_suite/unit_tests/Scripting/testNasalSys.hxx

@@ -38,6 +38,8 @@ class NasalSysTests : public CppUnit::TestFixture
     CPPUNIT_TEST(testRoundFloor);
     CPPUNIT_TEST(testRange);
     CPPUNIT_TEST(testKeywordArgInHash);
+    CPPUNIT_TEST(testNullAccess);
+    CPPUNIT_TEST(testNullishChain);
     CPPUNIT_TEST_SUITE_END();
 
 public:
@@ -55,6 +57,8 @@ public:
     void testRoundFloor();
     void testRange();
     void testKeywordArgInHash();
+    void testNullAccess();
+    void testNullishChain();
 };
 
 #endif  // _FG_NASALSYS_UNIT_TESTS_HXX