Add subspan unit test.

Author: j4james

src/terminal/parser/ut_parser/StateMachineTest.cpp

@@ -157,6 +157,8 @@ class Microsoft::Console::VirtualTerminal::StateMachineTest
     TEST_METHOD(PassThroughUnhandledSplitAcrossWrites);
 
     TEST_METHOD(DcsDataStringsReceivedByHandler);
+
+    TEST_METHOD(VtParameterSubspanTest);
 };
 
 void StateMachineTest::TwoStateMachinesDoNotInterfereWithEachOther()
@@ -337,3 +339,38 @@ void StateMachineTest::DcsDataStringsReceivedByHandler()
     // Verify the control characters were executed (if expected).
     VERIFY_ARE_EQUAL(expectedExecuted, engine.executed);
 }
+
+void StateMachineTest::VtParameterSubspanTest()
+{
+    const auto parameterList = std::vector<VTParameter>{ 12, 34, 56, 78 };
+    const auto parameterSpan = VTParameters{ parameterList.data(), parameterList.size() };
+
+    {
+        Log::Comment(L"Subspan from 0 gives all the parameters");
+        const auto subspan = parameterSpan.subspan(0);
+        VERIFY_ARE_EQUAL(4u, subspan.size());
+        VERIFY_ARE_EQUAL(12, subspan.at(0));
+        VERIFY_ARE_EQUAL(34, subspan.at(1));
+        VERIFY_ARE_EQUAL(56, subspan.at(2));
+        VERIFY_ARE_EQUAL(78, subspan.at(3));
+    }
+    {
+        Log::Comment(L"Subspan from 2 gives the last 2 parameters");
+        const auto subspan = parameterSpan.subspan(2);
+        VERIFY_ARE_EQUAL(2u, subspan.size());
+        VERIFY_ARE_EQUAL(56, subspan.at(0));
+        VERIFY_ARE_EQUAL(78, subspan.at(1));
+    }
+    {
+        Log::Comment(L"Subspan at the end of the range gives 1 omitted value");
+        const auto subspan = parameterSpan.subspan(4);
+        VERIFY_ARE_EQUAL(1u, subspan.size());
+        VERIFY_IS_FALSE(subspan.at(0).has_value());
+    }
+    {
+        Log::Comment(L"Subspan past the end of the range gives 1 omitted value");
+        const auto subspan = parameterSpan.subspan(6);
+        VERIFY_ARE_EQUAL(1u, subspan.size());
+        VERIFY_IS_FALSE(subspan.at(0).has_value());
+    }
+}