test: exploreUtils (#13719)

* Tests for exploreUtils

* removing eslint-disable

* applying factory

* Removing skip tests and code comments.

* Improving test name

* remove comments

* Improving "shouldUseLegacyApi" tests

* fixing typo

superset-frontend/src/explore/exploreUtils/getSimpleSQLExpression.test.ts

@@ -0,0 +1,62 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+import { getSimpleSQLExpression } from '.';
+
+const params = {
+  subject: 'subject',
+  operator: 'operator',
+  comparator: 'comparator',
+};
+
+test('Should return "" if subject is falsy', () => {
+  expect(getSimpleSQLExpression('', params.operator, params.comparator)).toBe(
+    '',
+  );
+  expect(getSimpleSQLExpression(null, params.operator, params.comparator)).toBe(
+    '',
+  );
+  expect(
+    getSimpleSQLExpression(undefined, params.operator, params.comparator),
+  ).toBe('');
+});
+
+test('Should return subject if operator is falsy', () => {
+  expect(getSimpleSQLExpression(params.subject, '', params.comparator)).toBe(
+    params.subject,
+  );
+  expect(getSimpleSQLExpression(params.subject, null, params.comparator)).toBe(
+    params.subject,
+  );
+  expect(
+    getSimpleSQLExpression(params.subject, undefined, params.comparator),
+  ).toBe(params.subject);
+});
+
+test('Should return correct string when subject and operator are valid values', () => {
+  expect(
+    getSimpleSQLExpression(params.subject, params.operator, params.comparator),
+  ).toBe("subject operator 'comparator'");
+
+  expect(
+    getSimpleSQLExpression(params.subject, params.operator, [
+      params.comparator,
+      'comparator-2',
+    ]),
+  ).toBe("subject operator 'comparator', 'comparator-2'");
+});