Avoid nullability warnings w/ new XUnit.Assert

test/Microsoft.Data.Sqlite.Tests/SqliteCommandTest.cs

@@ -49,6 +49,7 @@ public void CommandText_coalesces_to_empty()
                 CommandText = null
             };
 
+            Assert.NotNull(command.CommandText);
             Assert.Empty(command.CommandText);
         }
 

test/Microsoft.Data.Sqlite.Tests/SqliteConnectionStringBuilderTest.cs

@@ -86,6 +86,7 @@ public void ConnectionString_coalesces_to_empty()
                 ConnectionString = null
             };
 
+            Assert.NotNull(builder.ConnectionString);
             Assert.Empty(builder.ConnectionString);
         }
 

test/Microsoft.Data.Sqlite.Tests/SqliteConnectionTest.cs

@@ -41,6 +41,7 @@ public void ConnectionString_coalesces_to_empty()
                 ConnectionString = null
             };
 
+            Assert.NotNull(connection.ConnectionString);
             Assert.Empty(connection.ConnectionString);
         }
 

test/Microsoft.Data.Sqlite.Tests/SqliteParameterTest.cs

@@ -49,6 +49,7 @@ public void ParameterName_coalesces_to_empty()
                 ParameterName = null
             };
 
+            Assert.NotNull(parameter.ParameterName);
             Assert.Empty(parameter.ParameterName);
         }
 
@@ -68,6 +69,7 @@ public void SourceColumn_coalesces_to_empty()
                 SourceColumn = null
             };
 
+            Assert.NotNull(parameter.SourceColumn);
             Assert.Empty(parameter.SourceColumn);
         }