Refactored the test names and used backtick identifiers.

core-kotlin/src/test/kotlin/com/baeldung/kotlin/junit5/CalculatorTest5.kt

@@ -7,12 +7,12 @@ class CalculatorTest5 {
     private val calculator = Calculator()
 
     @Test
-    fun whenAdding1and3_thenAnswerIs4() {
+    fun `Adding 1 and 3 should be eqaul to 4`() {
         Assertions.assertEquals(4, calculator.add(1, 3))
     }
 
     @Test
-    fun whenDividingBy0_thenErrorOccurs() {
+    fun `Dividing by zero should throw the DivideByZeroException`() {
         val exception = Assertions.assertThrows(DivideByZeroException::class.java) {
             calculator.divide(5, 0)
         }
@@ -21,7 +21,7 @@ class CalculatorTest5 {
     }
 
     @Test
-    fun whenSquaringNumbers_thenCorrectAnswerGiven() {
+    fun `The square of a number should be eqaul to that number multiplied in itself`() {
         Assertions.assertAll(
                 Executable { Assertions.assertEquals(1, calculator.square(1)) },
                 Executable { Assertions.assertEquals(4, calculator.square(2)) },
@@ -76,7 +76,7 @@ class CalculatorTest5 {
             Tag("logarithms")
     )
     @Test
-    fun whenIcalculateLog2Of8_thenIget3() {
+    fun `Log to base 2 of 8 should be equal to 3`() {
         Assertions.assertEquals(3.0, calculator.log(2, 8))
     }
 }

core-kotlin/src/test/kotlin/com/baeldung/kotlin/junit5/SimpleTest5.kt

@@ -5,15 +5,16 @@ import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Test
 
 class SimpleTest5 {
+
     @Test
-    fun whenEmptyList_thenListIsEmpty() {
+    fun `isEmpty should return true for empty lists`() {
         val list = listOf<String>()
         Assertions.assertTrue(list::isEmpty)
     }
 
     @Test
     @Disabled
-    fun when3equals4_thenTestFails() {
+    fun `JUnit should complain and report failed assertions`() {
         Assertions.assertEquals(3, 4) {
             "Three does not equal four"
         }