test: add test for Postgres NOTNULL expression

Author: manticore-projects

src/test/java/net/sf/jsqlparser/expression/operators/relational/IsNullExpressionTest.java

@@ -0,0 +1,14 @@
+package net.sf.jsqlparser.expression.operators.relational;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.test.TestUtils;
+import org.junit.jupiter.api.Test;
+
+class IsNullExpressionTest {
+
+    @Test
+    void testNotNullExpression() throws JSQLParserException {
+        String sqlStr = "select * from mytable where 1 notnull";
+        TestUtils.assertSqlCanBeParsedAndDeparsed(sqlStr, true);
+    }
+}