diff --git a/src/morphism.rs b/src/morphism.rs
index 31a8e31..6b921bf 100644
--- a/src/morphism.rs
+++ b/src/morphism.rs
@@ -32,12 +32,10 @@ impl MorphismType {
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>\\
 
 impl<Morphism: Clone> MorphismBase<Morphism> {
-    pub fn new() -> Self {
+    pub fn new(list_typeid: TypeID) -> Self {
         MorphismBase {
             morphisms: Vec::new(),
-
-            // FIXME: magic number
-            list_typeid: TypeID::Fun(10)
+            list_typeid
         }
     }
 
diff --git a/src/test/mod.rs b/src/test/mod.rs
index 29c14bc..41f5e71 100644
--- a/src/test/mod.rs
+++ b/src/test/mod.rs
@@ -7,4 +7,5 @@ pub mod pnf;
 pub mod subtype;
 pub mod substitution;
 pub mod unification;
+pub mod morphism;
 
diff --git a/src/test/morphism.rs b/src/test/morphism.rs
new file mode 100644
index 0000000..29eb5c7
--- /dev/null
+++ b/src/test/morphism.rs
@@ -0,0 +1,73 @@
+use {
+    crate::{dict::*, morphism::*}
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>\\
+
+#[test]
+fn test_morphism_path() {
+    let mut dict = TypeDict::new();
+    let mut base = MorphismBase::<u64>::new( dict.add_typename("Seq".into()) );
+
+    dict.add_varname("Radix".into());
+    dict.add_varname("SrcRadix".into());
+    dict.add_varname("DstRadix".into());
+
+    base.add_morphism(
+        MorphismType{
+            src_type: dict.parse("<Digit Radix> ~ Char").unwrap(),
+            dst_type: dict.parse("<Digit Radix> ~ ℤ_2^64 ~ machine.UInt64").unwrap()
+        },
+        11
+    );
+    base.add_morphism(
+        MorphismType{
+            src_type: dict.parse("<Digit Radix> ~ ℤ_2^64 ~ machine.UInt64").unwrap(),
+            dst_type: dict.parse("<Digit Radix> ~ Char").unwrap()
+        },
+        22
+    );
+    base.add_morphism(
+        MorphismType{
+            src_type: dict.parse("ℕ ~ <PosInt Radix BigEndian> ~ <Seq <Digit Radix>~ℤ_2^64~machine.UInt64>").unwrap(),
+            dst_type: dict.parse("ℕ ~ <PosInt Radix LittleEndian> ~ <Seq <Digit Radix>~ℤ_2^64~machine.UInt64>").unwrap()
+        },
+        333
+    );
+    base.add_morphism(
+        MorphismType{
+            src_type: dict.parse("ℕ ~ <PosInt Radix LittleEndian> ~ <Seq <Digit Radix>~ℤ_2^64~machine.UInt64>").unwrap(),
+            dst_type: dict.parse("ℕ ~ <PosInt Radix BigEndian> ~ <Seq <Digit Radix>~ℤ_2^64~machine.UInt64>").unwrap()
+        },
+        444
+    );
+    base.add_morphism(
+        MorphismType{
+            src_type: dict.parse("ℕ ~ <PosInt SrcRadix LittleEndian> ~ <Seq <Digit SrcRadix>~ℤ_2^64~machine.UInt64>").unwrap(),
+            dst_type: dict.parse("ℕ ~ <PosInt DstRadix LittleEndian> ~ <Seq <Digit DstRadix>~ℤ_2^64~machine.UInt64>").unwrap()
+        },
+        555
+    );
+
+
+    let path = base.find_morphism_path(MorphismType {
+        src_type: dict.parse("ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10> ~ Char>").unwrap(),
+        dst_type: dict.parse("ℕ ~ <PosInt 16 BigEndian> ~ <Seq <Digit 16> ~ Char>").unwrap()
+    });
+
+    assert_eq!(
+        path,
+
+        Some(
+            vec![
+                dict.parse("ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10> ~ Char>").unwrap().normalize(),
+                dict.parse("ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10> ~ ℤ_2^64 ~ machine.UInt64>").unwrap().normalize(),
+                dict.parse("ℕ ~ <PosInt 10 LittleEndian> ~ <Seq <Digit 10> ~ ℤ_2^64 ~ machine.UInt64>").unwrap().normalize(),
+                dict.parse("ℕ ~ <PosInt 16 LittleEndian> ~ <Seq <Digit 16> ~ ℤ_2^64 ~ machine.UInt64>").unwrap().normalize(),
+                dict.parse("ℕ ~ <PosInt 16 BigEndian> ~ <Seq <Digit 16> ~ ℤ_2^64 ~ machine.UInt64>").unwrap().normalize(),
+                dict.parse("ℕ ~ <PosInt 16 BigEndian> ~ <Seq <Digit 16> ~ Char>").unwrap().normalize(),
+            ]
+        )
+    );
+}
+