diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..63cfca8
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,4 @@
+* text=auto eol=lf
+*.java ident
+*.xml ident
+*.png binary
diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index 5ea8d3b..a9e5ef4 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -27,4 +27,4 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-jdk-${{ matrix.java }}-maven-
       - name: Build it with Maven
-        run: mvn -B verify
+        run: mvn -B verify -Pqulice
diff --git a/.pdd b/.pdd
index 06e33de..e395f75 100644
--- a/.pdd
+++ b/.pdd
@@ -1,7 +1,7 @@
 --source=.
 --verbose
 --exclude target/**/*
---exclude src/test/resources/**/*
+--exclude src/test/resources-binary/**/*
 --exclude .idea/**/*
 --rule min-words:15
 --rule min-estimate:15
diff --git a/pom.xml b/pom.xml
index f92f23f..be80762 100644
--- a/pom.xml
+++ b/pom.xml
@@ -133,6 +133,10 @@ OTHER DEALINGS IN THE SOFTWARE.
         <directory>${basedir}/src/test/resources</directory>
         <filtering>false</filtering>
       </testResource>
+      <testResource>
+        <directory>${basedir}/src/test/resources-binary</directory>
+        <filtering>false</filtering>
+      </testResource>
     </testResources>
     <plugins>
       <plugin>
@@ -230,6 +234,19 @@ OTHER DEALINGS IN THE SOFTWARE.
         </executions>
       </plugin>
     </plugins>
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <groupId>com.qulice</groupId>
+          <artifactId>qulice-maven-plugin</artifactId>
+          <configuration>
+            <excludes combine.children="append">
+              <exclude>checkstyle:/src/test/resources-binary/.*</exclude>
+            </excludes>
+          </configuration>
+        </plugin>
+      </plugins>
+    </pluginManagement>
   </build>
   <profiles>
     <profile>
diff --git a/src/test/java/org/cqfn/rio/file/WriteSubscriberTest.java b/src/test/java/org/cqfn/rio/file/WriteSubscriberTest.java
index 6cbd219..2b4b18b 100644
--- a/src/test/java/org/cqfn/rio/file/WriteSubscriberTest.java
+++ b/src/test/java/org/cqfn/rio/file/WriteSubscriberTest.java
@@ -36,7 +36,8 @@
 import java.util.Locale;
 import java.util.concurrent.Executors;
 import org.reactivestreams.Subscriber;
-import org.reactivestreams.tck.SubscriberBlackboxVerification;
+import org.reactivestreams.Subscription;
+import org.reactivestreams.tck.SubscriberWhiteboxVerification;
 import org.reactivestreams.tck.TestEnvironment;
 import org.testng.SkipException;
 import org.testng.annotations.BeforeClass;
@@ -46,6 +47,7 @@
  *
  * @since 1.0
  * @checkstyle MagicNumberCheck (500 lines)
+ * @checkstyle AnonInnerLengthCheck (500 lines)
  */
 @SuppressWarnings(
     {
@@ -53,7 +55,7 @@
         "PMD.JUnit4TestShouldUseBeforeAnnotation"
     }
 )
-public final class WriteSubscriberTest extends SubscriberBlackboxVerification<ByteBuffer> {
+public final class WriteSubscriberTest extends SubscriberWhiteboxVerification<ByteBuffer> {
 
     /**
      * Ctor.
@@ -62,33 +64,121 @@ public WriteSubscriberTest() {
         super(new TestEnvironment());
     }
 
-    @BeforeClass
-    public void setUp() {
-        if (System.getProperty("os.name").toLowerCase(Locale.US).contains("win")) {
-            throw new SkipException("Disabled for windows");
-        }
-    }
-
     @Override
-    public Subscriber<ByteBuffer> createSubscriber() {
+    public Subscriber<ByteBuffer> createSubscriber(
+        final WhiteboxSubscriberProbe<ByteBuffer> probe
+    ) {
         final Path tmp;
         try {
             tmp = Files.createTempFile(this.getClass().getSimpleName(), ".tmp");
             tmp.toFile().deleteOnExit();
-            return new WriteSubscriber(
-                FileChannel.open(tmp, Collections.singleton(StandardOpenOption.WRITE)),
-                WriteGreed.SINGLE,
-                Executors.newCachedThreadPool()
+            return new SubscriberWithProbe<>(
+                new WriteSubscriber(
+                    FileChannel.open(tmp, Collections.singleton(StandardOpenOption.WRITE)),
+                    WriteGreed.SINGLE,
+                    Executors.newCachedThreadPool()
+                ),
+                probe
             );
         } catch (final IOException err) {
             throw new UncheckedIOException(err);
         }
     }
 
+    @BeforeClass
+    public void setUp() {
+        if (System.getProperty("os.name").toLowerCase(Locale.US).contains("win")) {
+            throw new SkipException("Disabled for windows");
+        }
+    }
+
     @Override
     public ByteBuffer createElement(final int element) {
         final byte[] arr = new byte[1024];
         Arrays.fill(arr, (byte) element);
         return ByteBuffer.wrap(arr);
     }
+
+    /**
+     * Subscriber with probe.
+     * @param <T> Subscriber type
+     * @since 0.2
+     */
+    private static class SubscriberWithProbe<T> implements Subscriber<T> {
+
+        /**
+         * Target subscriber.
+         */
+        private final Subscriber<T> target;
+
+        /**
+         * Test probe.
+         */
+        private final WhiteboxSubscriberProbe<T> probe;
+
+        /**
+         * Ctor.
+         * @param target Subscriber
+         * @param probe For test
+         */
+        SubscriberWithProbe(final Subscriber<T> target,
+            final WhiteboxSubscriberProbe<T> probe) {
+            this.target = target;
+            this.probe = probe;
+        }
+
+        @Override
+        public void onSubscribe(final Subscription subscription) {
+            this.target.onSubscribe(subscription);
+            this.probe.registerOnSubscribe(new ProbePuppet(subscription));
+        }
+
+        @Override
+        public void onNext(final T next) {
+            this.target.onNext(next);
+            this.probe.registerOnNext(next);
+        }
+
+        @Override
+        public void onError(final Throwable err) {
+            this.target.onError(err);
+            this.probe.registerOnError(err);
+        }
+
+        @Override
+        public void onComplete() {
+            this.target.onComplete();
+            this.probe.registerOnComplete();
+        }
+    }
+
+    /**
+     * Puppet for subscriber probe.
+     * @since 0.2
+     */
+    private static class ProbePuppet implements SubscriberPuppet {
+
+        /**
+         * Actual subscription.
+         */
+        private final Subscription subscription;
+
+        /**
+         * New puppet.
+         * @param subscription Of subscriber
+         */
+        ProbePuppet(final Subscription subscription) {
+            this.subscription = subscription;
+        }
+
+        @Override
+        public void triggerRequest(final long elements) {
+            this.subscription.request(elements);
+        }
+
+        @Override
+        public void signalCancel() {
+            this.subscription.cancel();
+        }
+    }
 }
diff --git a/src/test/resources/file.bin b/src/test/resources-binary/file.bin
similarity index 100%
rename from src/test/resources/file.bin
rename to src/test/resources-binary/file.bin
diff --git a/src/test/resources/log4j.properties b/src/test/resources-binary/log4j.properties
similarity index 100%
rename from src/test/resources/log4j.properties
rename to src/test/resources-binary/log4j.properties