diff --git a/src/main/java/com/lmax/solana4j/encoding/SolanaSlot.java b/src/main/java/com/lmax/solana4j/encoding/SolanaSlot.java
index 9b1188f..3d6d089 100644
--- a/src/main/java/com/lmax/solana4j/encoding/SolanaSlot.java
+++ b/src/main/java/com/lmax/solana4j/encoding/SolanaSlot.java
@@ -16,7 +16,7 @@ final class SolanaSlot implements Slot
     {
         if (requireNonNull(bytes).length != SLOT_LENGTH)
         {
-            throw new IllegalStateException("invalid slot length. Expected length: " + SLOT_LENGTH);
+            throw new IllegalArgumentException("invalid slot length. Expected length: " + SLOT_LENGTH);
         }
         this.bytes = bytes.clone();
     }
diff --git a/src/test/java/com/lmax/solana4j/encoding/SolanaSlotTest.java b/src/test/java/com/lmax/solana4j/encoding/SolanaSlotTest.java
new file mode 100644
index 0000000..b596269
--- /dev/null
+++ b/src/test/java/com/lmax/solana4j/encoding/SolanaSlotTest.java
@@ -0,0 +1,92 @@
+package com.lmax.solana4j.encoding;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.BufferOverflowException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThatThrownBy;
+
+class SolanaSlotTest
+{
+    @Test
+    void throwsOnNullKey()
+    {
+        assertThatThrownBy(() ->
+                new SolanaSlot(null))
+                .isInstanceOf(NullPointerException.class);
+    }
+
+    @Test
+    void throwsOnInvalidBlockhashLength()
+    {
+        assertThatThrownBy(() ->
+                new SolanaSlot(new byte[0]))
+                .isInstanceOf(IllegalArgumentException.class);
+
+        assertThatThrownBy(() ->
+                new SolanaSlot(new byte[1]))
+                .isInstanceOf(IllegalArgumentException.class);
+
+        assertThatThrownBy(() ->
+                new SolanaSlot(new byte[7]))
+                .isInstanceOf(IllegalArgumentException.class);
+
+        assertThatThrownBy(() ->
+                new SolanaSlot(new byte[9]))
+                .isInstanceOf(IllegalArgumentException.class);
+    }
+
+    @Test
+    void supportsEquality()
+    {
+        final var a = new SolanaSlot(new byte[]{0, 0, 0, 0, 0, 0, 0, 1});
+        final var b = new SolanaSlot(new byte[]{0, 0, 0, 0, 0, 0, 2, 0});
+        final var c = new SolanaSlot(new byte[]{0, 0, 0, 0, 0, 0, 2, 0});
+        final var d = new SolanaSlot(new byte[]{0, 4, 0, 0, 0, 0, 0, 0});
+        final var e = new SolanaSlot(new byte[]{5, 0, 0, 0, 0, 0, 0, 0});
+
+        assertThat(a).isEqualTo(a);
+        assertThat(a).isNotEqualTo(b);
+        assertThat(a).isNotEqualTo(c);
+        assertThat(b).isEqualTo(c);
+        assertThat(d).isNotEqualTo(e);
+
+        assertThat(a.hashCode()).isEqualTo(a.hashCode());
+        assertThat(b.hashCode()).isEqualTo(c.hashCode());
+    }
+
+    @Test
+    void writesToByteBufferCleanly()
+    {
+        final var bytes = new byte[]{1, 2, 3, 4, 5, 6, 7, 8};
+        final var a = new SolanaSlot(bytes);
+
+        final var buffer = ByteBuffer.allocate(15);
+
+        buffer.put((byte) 55).put((byte) 56).put((byte) 57);
+
+        a.write(buffer);
+
+        assertThat(buffer.position()).isEqualTo(11);
+        assertThat(buffer.limit()).isEqualTo(15);
+
+        assertThat((int) buffer.array()[0]).isEqualTo(55);
+        assertThat((int) buffer.array()[1]).isEqualTo(56);
+        assertThat((int) buffer.array()[2]).isEqualTo(57);
+        assertThat(Arrays.compare(buffer.array(), 3, buffer.position(), bytes, 0, 8)).isZero();
+    }
+
+    @Test
+    void throwsOnBufferOverflow()
+    {
+        final var bytes = new byte[]{1, 2, 3, 4, 5, 6, 7, 8};
+        final var a = new SolanaSlot(bytes);
+
+        final var buffer = ByteBuffer.allocate(7);
+
+        assertThatThrownBy(() -> a.write(buffer)).isInstanceOf(BufferOverflowException.class);
+    }
+}
\ No newline at end of file