diff --git a/assertj-core/src/test/java/org/assertj/core/util/myArraysTest.java b/assertj-core/src/test/java/org/assertj/core/util/myArraysTest.java
new file mode 100644
index 0000000000..790d24f5bd
--- /dev/null
+++ b/assertj-core/src/test/java/org/assertj/core/util/myArraysTest.java
@@ -0,0 +1,25 @@
+package org.assertj.core.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class myArraysTest {
+
+  //boundary test
+  @Test
+  public void sizeOfTestSmallest(){ assertEquals(0, Arrays.sizeOf(new char[0])); }
+
+  @Test
+  public void sizeOfTestSecondSmallest(){ assertEquals(1, Arrays.sizeOf(new char[1])); }
+
+  @Test
+  public void sizeOfTestTypical(){ assertEquals(500, Arrays.sizeOf(new char[500])); }
+
+  @Test
+  public void sizeOfTestSecondBiggest(){ assertEquals(Integer.MAX_VALUE - 3, Arrays.sizeOf(new char[Integer.MAX_VALUE - 3])); }
+
+  @Test
+  public void sizeOfTestBiggest(){ assertEquals(Integer.MAX_VALUE - 2, Arrays.sizeOf(new char[Integer.MAX_VALUE - 2])); }
+
+}
diff --git a/assertj-core/src/test/java/org/assertj/core/util/myDateUtilTests.java b/assertj-core/src/test/java/org/assertj/core/util/myDateUtilTests.java
new file mode 100644
index 0000000000..aeb456b4c6
--- /dev/null
+++ b/assertj-core/src/test/java/org/assertj/core/util/myDateUtilTests.java
@@ -0,0 +1,68 @@
+/*
+ * Licensed 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.
+ *
+ * Copyright 2012-2025 the original author or authors.
+ */
+
+package org.assertj.core.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.util.DateUtil.parse;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+
+public class myDateUtilTests {
+  private static SimpleDateFormat dateFormatter;
+
+  private static String[] unparsableDates;
+  private static String[] parsibleDates;
+
+  @BeforeAll
+  public static void setupForTests(){
+    dateFormatter = new SimpleDateFormat("dd/MM/yyyy");
+    unparsableDates = new String[] {"00/00/0000", "1.2/1.1/15.63", "99/99/9999", "gr/eg/milk"};
+    parsibleDates = new String[] {"01/01/0001", "01/12/1970", "20/01/2038", "31/12/9999"};
+
+  }
+
+  //partition equivalence
+  @Test
+  public void parseTestExtremeMinimum() throws ParseException { assertThrows(RuntimeException.class, () -> parse(unparsableDates[0])); }
+
+  @Test
+  public void parseTestFloats() throws ParseException { assertThrows(RuntimeException.class, () -> parse(unparsableDates[1])); }
+
+  @Test
+  public void parseTest() throws ParseException { assertThrows(RuntimeException.class, () -> parse(unparsableDates[2])); }
+
+  @Test
+  public void parseTestExtremeMaximum() throws ParseException { assertThrows(RuntimeException.class, () -> parse(unparsableDates[3])); }
+
+  @Test
+  public void parseTestMinimum() throws ParseException { assertEquals(parse("0001-01-01"), dateFormatter.parse(parsibleDates[0])); }
+
+  @Test
+  public void parseTestTypical() throws ParseException{ assertEquals(parse("1970-12-01"), dateFormatter.parse(parsibleDates[1])); }
+
+  @Test
+  public void parseTestEpoch() throws ParseException{ assertEquals(parse("2038-01-20"), dateFormatter.parse(parsibleDates[2])); }
+
+  @Test
+  public void parseTestMax() throws ParseException{ assertEquals(parse("9999-12-31"), dateFormatter.parse(parsibleDates[3])); }
+}
+
+
diff --git a/assertj-core/src/test/java/org/assertj/core/util/myStringsTests.java b/assertj-core/src/test/java/org/assertj/core/util/myStringsTests.java
new file mode 100644
index 0000000000..39a197d9e2
--- /dev/null
+++ b/assertj-core/src/test/java/org/assertj/core/util/myStringsTests.java
@@ -0,0 +1,82 @@
+/*
+ * Licensed 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.
+ *
+ * Copyright 2012-2025 the original author or authors.
+ */
+
+package org.assertj.core.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvFileSource;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+class myStringsTests {
+
+  private static String[] escapeCharacters;
+  private static String[] typicalStrings;
+  private static String[] stringsForPercentEscape;
+
+  @BeforeAll
+  static public void setUp(){
+    escapeCharacters = new String[] {"\n", "\t", "\b", "\'", "\""};
+    typicalStrings = new String[] {"Writing strings is so much fun", Character.toString(0)};
+    stringsForPercentEscape = new String[] {"This is a string", "%", "This sentence %has a percent in it", "%This %sentence %has %lots of percents %in it", "╫╦£æ₧", "%╫%╦£æ%₧", "\b%Backspaced character"};
+  }
+
+  @Test
+  public void quotesAroundObjectsTestBool(){ assertEquals(true, Strings.quote(true)); }
+
+  @Test
+  public void quotesAroundObjectsTestShort(){ assertEquals(Short.MIN_VALUE, Strings.quote(Short.MIN_VALUE)); }
+
+  @Test
+  public void quotesAroundObjectsTestDoubleMin() { assertEquals(Double.MIN_VALUE, Strings.quote(Double.MIN_VALUE)); }
+
+  @Test
+  public void quotesAroundObjectsTestDoubleMax(){ assertEquals(Double.MAX_VALUE, Strings.quote(Double.MAX_VALUE)); }
+
+  @Test
+  public void quotesAroundObjectsEmptyString(){ assertEquals("''", Strings.quote("")); }
+
+  @Test
+  public void escapePercentTestNull(){ assertEquals(null, Strings.escapePercent(null)); }
+
+  @Test
+  public void escapePercentTestNoPercent(){ assertEquals("This is a string", Strings.escapePercent(stringsForPercentEscape[0])); }
+
+  @Test
+  public void escapePercentTestSinglePercent(){ assertEquals("%%", Strings.escapePercent(stringsForPercentEscape[1])); }
+
+  @Test
+  public void escapePercentTestPercentInString(){ assertEquals("This sentence %%has a percent in it", Strings.escapePercent(stringsForPercentEscape[2])); }
+
+  @Test
+  public void escapePercentTestPercentsInString(){ assertEquals("%%This %%sentence %%has %%lots of percents %%in it", Strings.escapePercent(stringsForPercentEscape[3])); }
+
+  @Test
+  public void escapePercentTestSpecialString(){ assertEquals("╫╦£æ₧", Strings.escapePercent(stringsForPercentEscape[4])); }
+
+  @Test
+  public void escapePercentTestSpecialStringWithPercents(){ assertEquals("%%╫%%╦£æ%%₧", Strings.escapePercent(stringsForPercentEscape[5])); }
+
+  @Test
+  public void escapePercentTestEscapeSequenceString(){ assertEquals("\b%%Backspaced character", Strings.escapePercent(stringsForPercentEscape[6])); }
+}
+