diff --git a/jhdf/src/main/java/io/jhdf/Constants.java b/jhdf/src/main/java/io/jhdf/Constants.java
index e9d1d055..ad043500 100644
--- a/jhdf/src/main/java/io/jhdf/Constants.java
+++ b/jhdf/src/main/java/io/jhdf/Constants.java
@@ -16,6 +16,10 @@
  */
 public final class Constants {
 
+	private Constants() {
+		throw new AssertionError("No instances of Constants");
+	}
+
 	public static final byte NULL = '\0';
 
 	public static final byte SPACE = ' ';
@@ -25,6 +29,4 @@ public final class Constants {
 
 	public static final String PATH_SEPARATOR = "/";
 
-	private Constants() {
-	} // No instances
 }
diff --git a/jhdf/src/main/java/io/jhdf/Utils.java b/jhdf/src/main/java/io/jhdf/Utils.java
index f323223d..58909353 100644
--- a/jhdf/src/main/java/io/jhdf/Utils.java
+++ b/jhdf/src/main/java/io/jhdf/Utils.java
@@ -25,7 +25,7 @@ public final class Utils {
 	private static final CharsetEncoder ASCII = StandardCharsets.US_ASCII.newEncoder();
 
 	private Utils() {
-		// No instances
+		throw new AssertionError("No instances of Utils");
 	}
 
 	/**
diff --git a/jhdf/src/main/java/io/jhdf/dataset/CompoundDatasetReader.java b/jhdf/src/main/java/io/jhdf/dataset/CompoundDatasetReader.java
index 5bf76a54..29a59521 100644
--- a/jhdf/src/main/java/io/jhdf/dataset/CompoundDatasetReader.java
+++ b/jhdf/src/main/java/io/jhdf/dataset/CompoundDatasetReader.java
@@ -21,8 +21,8 @@
 
 public final class CompoundDatasetReader {
 
-	/** No instances */
 	private CompoundDatasetReader() {
+		throw new AssertionError("No instances of CompoundDatasetReader");
 	}
 
 	public static Map<String, Object> readDataset(CompoundDataType type, ByteBuffer buffer, int[] dimensions, HdfFileChannel hdfFc) {
diff --git a/jhdf/src/main/java/io/jhdf/dataset/DatasetLoader.java b/jhdf/src/main/java/io/jhdf/dataset/DatasetLoader.java
index 7bf0d9ec..24f8d3a2 100644
--- a/jhdf/src/main/java/io/jhdf/dataset/DatasetLoader.java
+++ b/jhdf/src/main/java/io/jhdf/dataset/DatasetLoader.java
@@ -25,7 +25,7 @@
 public final class DatasetLoader {
 
 	private DatasetLoader() {
-		// No instances
+		throw new AssertionError("No instances of DatasetLoader");
 	}
 
 	public static Dataset createDataset(HdfFileChannel hdfFc, ObjectHeader oh, String name,
diff --git a/jhdf/src/main/java/io/jhdf/dataset/DatasetReader.java b/jhdf/src/main/java/io/jhdf/dataset/DatasetReader.java
index fd14fcdb..251ca0ef 100644
--- a/jhdf/src/main/java/io/jhdf/dataset/DatasetReader.java
+++ b/jhdf/src/main/java/io/jhdf/dataset/DatasetReader.java
@@ -36,7 +36,6 @@
  */
 public final class DatasetReader {
 
-	/** No instances */
 	private DatasetReader() {
 		throw new AssertionError("No instances of DatasetReader");
 	}
diff --git a/jhdf/src/main/java/io/jhdf/dataset/VariableLengthDatasetReader.java b/jhdf/src/main/java/io/jhdf/dataset/VariableLengthDatasetReader.java
index 1033f08d..e2f6632d 100644
--- a/jhdf/src/main/java/io/jhdf/dataset/VariableLengthDatasetReader.java
+++ b/jhdf/src/main/java/io/jhdf/dataset/VariableLengthDatasetReader.java
@@ -29,8 +29,8 @@
 
 public final class VariableLengthDatasetReader {
 
-	/** No instances */
 	private VariableLengthDatasetReader() {
+		throw new AssertionError("No instances of VariableLengthDatasetReader");
 	}
 
 	public static Object readDataset(VariableLength type, ByteBuffer buffer, int[] dimensions, HdfFileChannel hdfFc) {
diff --git a/jhdf/src/test/java/io/jhdf/NoInstancesTest.java b/jhdf/src/test/java/io/jhdf/NoInstancesTest.java
new file mode 100644
index 00000000..fc135cac
--- /dev/null
+++ b/jhdf/src/test/java/io/jhdf/NoInstancesTest.java
@@ -0,0 +1,46 @@
+/*
+ * This file is part of jHDF. A pure Java library for accessing HDF5 files.
+ *
+ * http://jhdf.io
+ *
+ * Copyright (c) 2020 James Mudd
+ *
+ * MIT License see 'LICENSE' file
+ */
+package io.jhdf;
+
+import io.jhdf.dataset.CompoundDatasetReader;
+import io.jhdf.dataset.DatasetLoader;
+import io.jhdf.dataset.DatasetReader;
+import io.jhdf.dataset.EnumDatasetReader;
+import io.jhdf.dataset.VariableLengthDatasetReader;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.powermock.reflect.Whitebox.invokeConstructor;
+
+class NoInstancesTest {
+
+	static Stream<Arguments> noInstances() {
+		return Stream.of(
+				Arguments.of(DatasetLoader.class),
+				Arguments.of(DatasetReader.class),
+				Arguments.of(CompoundDatasetReader.class),
+				Arguments.of(EnumDatasetReader.class),
+				Arguments.of(VariableLengthDatasetReader.class),
+				Arguments.of(Constants.class),
+				Arguments.of(Utils.class)
+		);
+	}
+
+	@ParameterizedTest
+	@MethodSource
+	void noInstances(Class<?> clazz) {
+		assertThrows(AssertionError.class, () -> invokeConstructor(clazz));
+	}
+
+}
diff --git a/jhdf/src/test/java/io/jhdf/dataset/DatasetLoaderTest.java b/jhdf/src/test/java/io/jhdf/dataset/DatasetLoaderTest.java
new file mode 100644
index 00000000..b1b9a25d
--- /dev/null
+++ b/jhdf/src/test/java/io/jhdf/dataset/DatasetLoaderTest.java
@@ -0,0 +1,67 @@
+/*
+ * This file is part of jHDF. A pure Java library for accessing HDF5 files.
+ *
+ * http://jhdf.io
+ *
+ * Copyright (c) 2020 James Mudd
+ *
+ * MIT License see 'LICENSE' file
+ */
+package io.jhdf.dataset;
+
+import io.jhdf.HdfFileChannel;
+import io.jhdf.ObjectHeader;
+import io.jhdf.api.Group;
+import io.jhdf.exceptions.HdfException;
+import io.jhdf.object.message.DataLayout;
+import io.jhdf.object.message.DataLayoutMessage;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import java.util.BitSet;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.powermock.reflect.Whitebox.invokeConstructor;
+
+class DatasetLoaderTest {
+
+	@Test
+	void testUnrecognisedDataLayoutMessage() {
+		HdfFileChannel hdfFileChannel = mock(HdfFileChannel.class);
+		ObjectHeader objectHeader = mock(ObjectHeader.class);
+		String name = "test";
+		Group group = mock(Group.class);
+
+		when(objectHeader.getMessageOfType(DataLayoutMessage.class))
+				.thenReturn(new UnknownDataLayoutMessage(new BitSet()));
+
+		assertThrows(HdfException.class, () -> DatasetLoader.createDataset(hdfFileChannel, objectHeader, name, group));
+	}
+
+	@Test
+	void testFailureToReadDataset() {
+		HdfFileChannel hdfFileChannel = mock(HdfFileChannel.class);
+		ObjectHeader objectHeader = mock(ObjectHeader.class);
+		String name = "test";
+		Group group = mock(Group.class);
+
+		when(objectHeader.getMessageOfType(DataLayoutMessage.class))
+				.thenThrow(RuntimeException.class);
+
+		assertThrows(HdfException.class, () -> DatasetLoader.createDataset(hdfFileChannel, objectHeader, name, group));
+	}
+
+	private static class UnknownDataLayoutMessage extends DataLayoutMessage {
+
+		public UnknownDataLayoutMessage(BitSet flags) {
+			super(flags);
+		}
+
+		@Override
+		public DataLayout getDataLayout() {
+			return null;
+		}
+	}
+}