testing: improve test coverage DuplicateBracketsTest (#6396)

* testing: improve test coverage DuplicateBracketsTest

* style: fix formatting checkstyle

* style: fix formatting checkstyle

---------

Co-authored-by: Deniz Altunkapan <93663085+DenizAltunkapan@users.noreply.github.com>

src/test/java/com/thealgorithms/stacks/DuplicateBracketsTest.java

@@ -4,20 +4,23 @@ import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import java.util.stream.Stream;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.MethodSource;
 
 class DuplicateBracketsTest {
 
     @ParameterizedTest
-    @CsvSource({"'((a + b) + (c + d))'", "'(a + b)'", "'a + b'", "'('", "''"})
+    @CsvSource({"'((a + b) + (c + d))'", "'(a + b)'", "'a + b'", "'('", "''", "'a + (b * c) - d'", "'(x + y) * (z)'", "'(a + (b - c))'"})
     void testInputReturnsFalse(String input) {
         assertFalse(DuplicateBrackets.check(input));
     }
 
     @ParameterizedTest
-    @CsvSource({"'(a + b) + ((c + d))'", "'((a + b))'", "'((((a + b)))))'"})
+    @CsvSource({"'(a + b) + ((c + d))'", "'((a + b))'", "'((((a + b)))))'", "'((x))'", "'((a + (b)))'", "'(a + ((b)))'", "'(((a)))'", "'(((())))'"})
     void testInputReturnsTrue(String input) {
         assertTrue(DuplicateBrackets.check(input));
     }
@@ -26,4 +29,27 @@ class DuplicateBracketsTest {
     void testInvalidInput() {
         assertThrows(IllegalArgumentException.class, () -> DuplicateBrackets.check(null));
     }
+
+    @ParameterizedTest(name = "Should be true: \"{0}\"")
+    @MethodSource("provideInputsThatShouldReturnTrue")
+    void testDuplicateBracketsTrueCases(String input) {
+        assertTrue(DuplicateBrackets.check(input));
+    }
+
+    static Stream<Arguments> provideInputsThatShouldReturnTrue() {
+        return Stream.of(Arguments.of("()"), Arguments.of("(( ))"));
+    }
+
+    @ParameterizedTest(name = "Should be false: \"{0}\"")
+    @MethodSource("provideInputsThatShouldReturnFalse")
+    void testDuplicateBracketsFalseCases(String input) {
+        assertFalse(DuplicateBrackets.check(input));
+    }
+
+    static Stream<Arguments> provideInputsThatShouldReturnFalse() {
+        return Stream.of(Arguments.of("( )"), // whitespace inside brackets
+            Arguments.of("abc + def"), // no brackets
+            Arguments.of("(a + (b * c)) - (d / e)") // complex, but no duplicates
+        );
+    }
 }