diff --git a/core/src/test/java/hudson/FilePathTest.java b/core/src/test/java/hudson/FilePathTest.java
index 79ad7816e88558a6512d3dd4a4ddddcfe22bb2ea..73d0b6fcc7077b835a9101bc1a7a1764ed552dd3 100644
--- a/core/src/test/java/hudson/FilePathTest.java
+++ b/core/src/test/java/hudson/FilePathTest.java
@@ -54,7 +54,13 @@ import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
 
 import static org.hamcrest.CoreMatchers.is;
-import static org.junit.Assert.*;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 import static org.junit.Assume.assumeFalse;
 import static org.junit.Assume.assumeTrue;
 import static org.mockito.Mockito.*;
@@ -293,7 +299,7 @@ public class FilePathTest {
     }
 
     @Issue("JENKINS-6494")
-    @Test public void getParent() throws Exception {
+    @Test public void getParent() {
         FilePath fp = new FilePath((VirtualChannel)null, "/abc/def");
         assertEquals("/abc", (fp = fp.getParent()).getRemote());
         assertEquals("/", (fp = fp.getParent()).getRemote());
@@ -491,7 +497,7 @@ public class FilePathTest {
     }
 
     @Issue("JENKINS-13649")
-    @Test public void multiSegmentRelativePaths() throws Exception {
+    @Test public void multiSegmentRelativePaths() {
         VirtualChannel d = Mockito.mock(VirtualChannel.class);
         FilePath winPath = new FilePath(d, "c:\\app\\jenkins\\workspace");
         FilePath nixPath = new FilePath(d, "/opt/jenkins/workspace");
diff --git a/core/src/test/java/hudson/util/ArgumentListBuilderTest.java b/core/src/test/java/hudson/util/ArgumentListBuilderTest.java
index e8c58e73fcf6c8d1a694feefc299a788f0a1157b..a04c8211b00f6bd566daed8f3b07eff1d46d2593 100644
--- a/core/src/test/java/hudson/util/ArgumentListBuilderTest.java
+++ b/core/src/test/java/hudson/util/ArgumentListBuilderTest.java
@@ -23,8 +23,12 @@
  */
 package hudson.util;
 
-import static org.junit.Assert.*;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 import java.util.HashMap;
diff --git a/core/src/test/java/hudson/util/AtomicFileWriterTest.java b/core/src/test/java/hudson/util/AtomicFileWriterTest.java
index e36a325c5bce79c8dc08035d87c0d8ddad9a7a7f..72e64746a1e721801e1ba68659d6a1b7cc661218 100644
--- a/core/src/test/java/hudson/util/AtomicFileWriterTest.java
+++ b/core/src/test/java/hudson/util/AtomicFileWriterTest.java
@@ -22,9 +22,9 @@ import java.util.Set;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.StringContains.containsString;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.junit.Assume.assumeThat;
@@ -86,7 +86,7 @@ public class AtomicFileWriterTest {
     }
 
     @Test
-    public void createFile() throws Exception {
+    public void createFile() {
         // Verify the file we created exists
         assertTrue(Files.exists(afw.getTemporaryPath()));
     }
@@ -163,7 +163,7 @@ public class AtomicFileWriterTest {
 
     @Issue("JENKINS-48407")
     @Test
-    public void checkPermissionsRespectUmask() throws IOException, InterruptedException {
+    public void checkPermissionsRespectUmask() throws IOException {
 
         final File newFile = tmp.newFile();
         boolean posixSupported = isPosixSupported(newFile);
diff --git a/core/src/test/java/hudson/util/FileChannelWriterTest.java b/core/src/test/java/hudson/util/FileChannelWriterTest.java
index b61cce1473b9fa86aefed638c4afbf4429c5e1a2..9d0a86675fc7e337779f73ef6ba90dbe4735b175 100644
--- a/core/src/test/java/hudson/util/FileChannelWriterTest.java
+++ b/core/src/test/java/hudson/util/FileChannelWriterTest.java
@@ -13,7 +13,7 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.StandardOpenOption;
 
 import static org.hamcrest.core.IsEqual.equalTo;
-import static org.junit.Assert.assertThat;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.fail;
 
 public class FileChannelWriterTest {
diff --git a/core/src/test/java/jenkins/security/ClassFilterImplSanityTest.java b/core/src/test/java/jenkins/security/ClassFilterImplSanityTest.java
index 7a710aaeb4ae0c0119395b6d7fed84a387dbd4e5..a917de92a0cb3ce4980c170e7dc56d41399e082c 100644
--- a/core/src/test/java/jenkins/security/ClassFilterImplSanityTest.java
+++ b/core/src/test/java/jenkins/security/ClassFilterImplSanityTest.java
@@ -32,7 +32,7 @@ import java.util.stream.Collectors;
 import jenkins.util.MemoryReductionUtil;
 import org.apache.commons.io.IOUtils;
 import static org.hamcrest.Matchers.*;
-import static org.junit.Assert.assertThat;
+import static org.hamcrest.MatcherAssert.assertThat;
 import org.junit.Test;
 import org.jvnet.hudson.test.For;
 
diff --git a/core/src/test/java/jenkins/security/DefaultConfidentialStoreTest.java b/core/src/test/java/jenkins/security/DefaultConfidentialStoreTest.java
index f78c4969642eaf927b15ac5556639435b522946f..b7e3961473be67beb911859bcf86c1aba90a7965 100644
--- a/core/src/test/java/jenkins/security/DefaultConfidentialStoreTest.java
+++ b/core/src/test/java/jenkins/security/DefaultConfidentialStoreTest.java
@@ -7,7 +7,11 @@ import java.nio.charset.Charset;
 
 import org.apache.commons.io.FileUtils;
 import static org.hamcrest.CoreMatchers.*;
-import static org.junit.Assert.*;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
diff --git a/core/src/test/java/jenkins/security/apitoken/ApiTokenStatsTest.java b/core/src/test/java/jenkins/security/apitoken/ApiTokenStatsTest.java
index 1c1be386c2934ce00c2eb3dc8afa30c8cd229ba4..9c95c910d4fb6909652656024f2663e0606ae8ce 100644
--- a/core/src/test/java/jenkins/security/apitoken/ApiTokenStatsTest.java
+++ b/core/src/test/java/jenkins/security/apitoken/ApiTokenStatsTest.java
@@ -52,10 +52,10 @@ import java.util.UUID;
 import java.util.stream.Collectors;
 
 import static org.hamcrest.Matchers.*;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertThat;
 
 @RunWith(PowerMockRunner.class)
 @PrepareForTest(ApiTokenPropertyConfiguration.class)
@@ -108,6 +108,7 @@ public class ApiTokenStatsTest {
             lastUsage = stats.getLastUseDate();
             assertNotNull(lastUsage);
             // to avoid flaky test in case the test is run at midnight, normally it's 0 
+            
             assertThat(stats.getNumDaysUse(), lessThanOrEqualTo(1L));
         }
         
@@ -164,7 +165,7 @@ public class ApiTokenStatsTest {
     }
     
     @Test
-    public void testResilientIfFileDoesNotExist() throws Exception {
+    public void testResilientIfFileDoesNotExist() {
         ApiTokenStats tokenStats = createFromFile(tmp.getRoot());
         assertNotNull(tokenStats);
     }
@@ -193,7 +194,7 @@ public class ApiTokenStatsTest {
             String content = FileUtils.readFileToString(statsFile.getFile(), Charset.defaultCharset());
             // now there are multiple times the same id in the file with different stats
             String newContentWithDuplicatedId = content.replace(ID_1, ID_2).replace(ID_3, ID_2);
-            FileUtils.write(statsFile.getFile(), newContentWithDuplicatedId);
+            FileUtils.write(statsFile.getFile(), newContentWithDuplicatedId, Charset.defaultCharset());
         }
         
         {