diff --git a/members/libpt-bintols/tests/join.rs b/members/libpt-bintols/tests/join.rs
new file mode 100644
index 0000000..35a76c7
--- /dev/null
+++ b/members/libpt-bintols/tests/join.rs
@@ -0,0 +1,55 @@
+use libpt_bintols::join::*;
+
+#[test]
+fn join_u128() {
+    let correct = [
+        16,
+        255,
+        256,
+        0,
+        u128::MAX,
+        u64::MAX as u128,
+        u64::MAX as u128 + 1,
+    ];
+    let source = [
+        vec![16],
+        vec![255],
+        vec![1, 0],
+        vec![0],
+        vec![
+            255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+        ],
+        vec![255, 255, 255, 255, 255, 255, 255, 255],
+        vec![1, 0, 0, 0, 0, 0, 0, 0, 0],
+    ];
+    for (i, n) in source.iter().enumerate() {
+        assert_eq!(array_to_unsigned::<u128>(n).unwrap(), correct[i]);
+    }
+}
+
+#[test]
+fn join_u64() {
+    let correct = [
+        16,
+        255,
+        256,
+        0,
+        u64::MAX,
+        u32::MAX as u64,
+        0b1_00000001,
+        0b10011011_10110101_11110000_00110011,
+    ];
+    let source = [
+        vec![16],
+        vec![255],
+        vec![1, 0],
+        vec![0],
+        vec![255, 255, 255, 255, 255, 255, 255, 255],
+        vec![255, 255, 255, 255],
+        vec![1, 1],
+        vec![0b10011011, 0b10110101, 0b11110000, 0b00110011],
+    ];
+    for (i, n) in source.iter().enumerate() {
+        assert_eq!(array_to_unsigned::<u64>(n).unwrap(), correct[i]);
+    }
+}