diff --git a/guava/src/test/java/org/baeldung/guava/GuavaPreConditionsTest.java b/guava/src/test/java/org/baeldung/guava/GuavaPreConditionsTest.java
index 55e3c7db00..aff42ea6e2 100644
--- a/guava/src/test/java/org/baeldung/guava/GuavaPreConditionsTest.java
+++ b/guava/src/test/java/org/baeldung/guava/GuavaPreConditionsTest.java
@@ -3,7 +3,7 @@ package org.baeldung.guava;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import java.util.Arrays;
 import org.junit.Test;
-import static com.google.common.base.Preconditions.*;
+import com.google.common.base.*;
 
 public class GuavaPreConditionsTest {
 
@@ -11,10 +11,7 @@ public class GuavaPreConditionsTest {
     public void whenCheckArgumentEvaluatesFalse_throwsException() {
         int age = -18;
 
-        assertThatThrownBy(() -> checkArgument(age > 0))
-            .isInstanceOf(IllegalArgumentException.class)
-            .hasMessage(null)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkArgument(age > 0)).isInstanceOf(IllegalArgumentException.class).hasMessage(null).hasNoCause();
     }
 
     @Test
@@ -22,10 +19,7 @@ public class GuavaPreConditionsTest {
         final int age = -18;
         final String message = "Age can't be zero or less than zero";
 
-        assertThatThrownBy(() -> checkArgument(age > 0, message))
-            .isInstanceOf(IllegalArgumentException.class)
-            .hasMessage(message)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkArgument(age > 0, message)).isInstanceOf(IllegalArgumentException.class).hasMessage(message).hasNoCause();
     }
 
     @Test
@@ -33,19 +27,14 @@ public class GuavaPreConditionsTest {
         final int age = -18;
         final String message = "Age can't be zero or less than zero, you supplied %s.";
 
-        assertThatThrownBy(() -> checkArgument(age > 0, message, age))
-            .isInstanceOf(IllegalArgumentException.class)
-            .hasMessage(message, age)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkArgument(age > 0, message, age)).isInstanceOf(IllegalArgumentException.class).hasMessage(message, age).hasNoCause();
     }
 
     @Test
     public void givenArrayOfIntegers_whenCheckElementIndexEvaluatesFalse_throwsException() {
         final int[] numbers = { 1, 2, 3, 4, 5 };
 
-        assertThatThrownBy(() -> checkElementIndex(6, numbers.length - 1))
-            .isInstanceOf(IndexOutOfBoundsException.class)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkElementIndex(6, numbers.length - 1)).isInstanceOf(IndexOutOfBoundsException.class).hasNoCause();
     }
 
     @Test
@@ -53,20 +42,7 @@ public class GuavaPreConditionsTest {
         final int[] numbers = { 1, 2, 3, 4, 5 };
         final String message = "Please check the bound of an array and retry";
 
-        assertThatThrownBy(() -> checkElementIndex(6, numbers.length - 1, message))
-            .isInstanceOf(IndexOutOfBoundsException.class)
-            .hasMessageStartingWith(message)
-            .hasNoCause();
-    }
-
-    @Test
-    public void givenNullString_whenCheckNotNullCalled_throwsException() {
-        final String nullObject = null;
-
-        assertThatThrownBy(() -> checkNotNull(nullObject))
-            .isInstanceOf(NullPointerException.class)
-            .hasMessage(null)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkElementIndex(6, numbers.length - 1, message)).isInstanceOf(IndexOutOfBoundsException.class).hasMessageStartingWith(message).hasNoCause();
     }
 
     @Test
@@ -74,10 +50,7 @@ public class GuavaPreConditionsTest {
         final String nullObject = null;
         final String message = "Please check the Object supplied, its null!";
 
-        assertThatThrownBy(() -> checkNotNull(nullObject, message))
-            .isInstanceOf(NullPointerException.class)
-            .hasMessage(message)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkNotNull(nullObject, message)).isInstanceOf(NullPointerException.class).hasMessage(message).hasNoCause();
     }
 
     @Test
@@ -85,19 +58,14 @@ public class GuavaPreConditionsTest {
         final String nullObject = null;
         final String message = "Please check the Object supplied, its %s!";
 
-        assertThatThrownBy(() -> checkNotNull(nullObject, message, nullObject))
-            .isInstanceOf(NullPointerException.class)
-            .hasMessage(message, nullObject)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkNotNull(nullObject, message, nullObject)).isInstanceOf(NullPointerException.class).hasMessage(message, nullObject).hasNoCause();
     }
 
     @Test
     public void givenArrayOfIntegers_whenCheckPositionIndexEvaluatesFalse_throwsException() {
         final int[] numbers = { 1, 2, 3, 4, 5 };
 
-        assertThatThrownBy(() -> checkPositionIndex(6, numbers.length - 1))
-            .isInstanceOf(IndexOutOfBoundsException.class)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkPositionIndex(6, numbers.length - 1)).isInstanceOf(IndexOutOfBoundsException.class).hasNoCause();
     }
 
     @Test
@@ -105,30 +73,14 @@ public class GuavaPreConditionsTest {
         final int[] numbers = { 1, 2, 3, 4, 5 };
         final String message = "Please check the bound of an array and retry";
 
-        assertThatThrownBy(() -> checkPositionIndex(6, numbers.length - 1, message))
-            .isInstanceOf(IndexOutOfBoundsException.class)
-            .hasMessageStartingWith(message)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkPositionIndex(6, numbers.length - 1, message)).isInstanceOf(IndexOutOfBoundsException.class).hasMessageStartingWith(message).hasNoCause();
     }
 
     @Test
     public void givenArrayOfIntegers_whenCheckPositionIndexesEvaluatesFalse_throwsException() {
         final int[] numbers = { 1, 2, 3, 4, 5 };
 
-        assertThatThrownBy(() -> checkPositionIndexes(6, 0, numbers.length - 1))
-            .isInstanceOf(IndexOutOfBoundsException.class)
-            .hasNoCause();
-    }
-
-    @Test
-    public void givenValidStates_whenCheckStateEvaluatesFalse_throwsException() {
-        final int[] validStates = { -1, 0, 1 };
-        final int givenState = 10;
-
-        assertThatThrownBy(() -> checkState(Arrays.binarySearch(validStates, givenState) > 0))
-            .isInstanceOf(IllegalStateException.class)
-            .hasMessage(null)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkPositionIndexes(6, 0, numbers.length - 1)).isInstanceOf(IndexOutOfBoundsException.class).hasNoCause();
     }
 
     @Test
@@ -137,10 +89,7 @@ public class GuavaPreConditionsTest {
         final int givenState = 10;
         final String message = "You have entered an invalid state";
 
-        assertThatThrownBy(() -> checkState(Arrays.binarySearch(validStates, givenState) > 0, message))
-            .isInstanceOf(IllegalStateException.class)
-            .hasMessageStartingWith(message)
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkState(Arrays.binarySearch(validStates, givenState) > 0, message)).isInstanceOf(IllegalStateException.class).hasMessageStartingWith(message).hasNoCause();
     }
 
     @Test
@@ -149,9 +98,7 @@ public class GuavaPreConditionsTest {
         final int givenState = 10;
         final String message = "State can't be %s, It can be one of %s.";
 
-        assertThatThrownBy(() -> checkState(Arrays.binarySearch(validStates, givenState) > 0, message, givenState, Arrays.toString(validStates)))
-            .isInstanceOf(IllegalStateException.class)
-            .hasMessage(message, givenState, Arrays.toString(validStates))
-            .hasNoCause();
+        assertThatThrownBy(() -> Preconditions.checkState(Arrays.binarySearch(validStates, givenState) > 0, message, givenState, Arrays.toString(validStates))).isInstanceOf(IllegalStateException.class)
+                .hasMessage(message, givenState, Arrays.toString(validStates)).hasNoCause();
     }
-}
+}
\ No newline at end of file