diff --git a/vade/src/NPuzzle/_test.py b/vade/src/NPuzzle/_test.py
new file mode 100644
index 0000000..66e2536
--- /dev/null
+++ b/vade/src/NPuzzle/_test.py
@@ -0,0 +1,227 @@
+import unittest
+from copy import deepcopy
+def gen(inp:list)->list:
+    a,b,c,d=[deepcopy(inp)for i in range(4)]
+    if inp[0][0]==0:
+        a[0][0],a[0][1]=a[0][1],a[0][0]
+        b[0][0],b[1][0]=b[1][0],b[0][0]
+        l=[a,b]
+    elif inp[0][1]==0:
+        a[0][1],a[0][0]=a[0][0],a[0][1]
+        b[0][1],b[0][2]=b[0][2],b[0][1]
+        c[0][1],c[1][1]=c[1][1],c[0][1]
+        l=[a,b,c]
+    elif inp[0][2]==0:
+        a[0][2],a[0][1]=a[0][1],a[0][2]
+        b[0][2],b[1][2]=b[1][2],b[0][2]
+        l=[a,b]
+    elif inp[1][0]==0:
+        a[1][0],a[1][1]=a[1][1],a[1][0]
+        b[1][0],b[0][0]=b[0][0],b[1][0]
+        c[1][0],c[2][0]=c[2][0],c[1][0]
+        l=[a,b,c]
+    elif inp[1][1]==0:
+        a[1][1],a[1][0]=a[1][0],a[1][1]
+        b[1][1],b[1][2]=b[1][2],b[1][1]
+        c[1][1],c[0][1]=c[0][1],c[1][1]
+        d[1][1],d[2][1]=d[2][1],d[1][1]
+        l=[a,b,c,d]
+    elif inp[1][2]==0:
+        a[1][2],a[1][1]=a[1][1],a[1][2]
+        b[1][2],b[0][2]=b[0][2],b[1][2]
+        c[1][2],c[2][2]=c[2][2],c[1][2]
+        l=[a,b,c]
+    elif inp[2][0]==0:
+        a[2][0],a[2][1]=a[2][1],a[2][0]
+        b[2][0],b[1][0]=b[1][0],b[2][0]
+        l=[a,b]
+    elif inp[2][1]==0:
+        a[2][1],a[2][0]=a[2][0],a[2][1]
+        b[2][1],b[2][2]=b[2][2],b[2][1]
+        c[2][1],c[1][1]=c[1][1],c[2][1]
+        l=[a,b,c]
+    elif inp[2][2]==0:
+        a[2][2],a[2][1]=a[2][1],a[2][2]
+        b[2][2],b[1][2]=b[1][2],b[2][2]
+        l=[a,b]
+    return l
+def disp_valid(l:list,last):
+    for e in l:
+        valid=e!=last
+        #print(f" {e},{'OP'if valid else'cl'}",end="")
+    #print()
+def get_next(l:list,last=None)->list:
+    #print(f"finding first non {last}")
+    for e in reversed(l):
+        if e!=last:
+            return e
+    0/0
+
+def dfs(inp0:list, goal:list)->int:
+    seen={}
+    #print()
+    return dfs_walk(inp0,goal, seen)
+
+def dfs_walk(inp0:list, goal:list, seen:dict, step=0)->int:
+    #print(f"step={step} inp0={inp0} seen={seen}")
+    #print(f"step={step} inp0={inp0} seen={len(seen)}")
+    if inp0==goal:
+        #print(f"found goal! seen={len(seen)}")
+        return step
+    sinp0=str(inp0)
+    if sinp0 in seen:
+        #print("already seen!")
+        return 0
+    seen[sinp0]=1
+    out=gen(inp0)
+    for inp in reversed(out):
+        #print(f"step={step} walking inp={inp} seen={seen}")
+        #print(f"step={step} walking inp={inp} seen={len(seen)}")
+        res=dfs_walk(inp, goal, seen, step+1)
+        if res>0:
+            #print(f"child found returned res={res}")
+            return res
+        #print("first try failed")
+        #0/0
+    #0/0
+    return 0
+
+def idfs_walk(inp0:list, goal:list, seen:dict, depth:int, step=0)->int:
+    if step>depth:
+        #print("too many steps!")
+        return 0
+    #print(f"step={step} depth={depth} inp0={inp0} seen={len(seen)}")
+    if inp0==goal:
+        #print(f"found goal! seen={len(seen)}")
+        return step
+    sinp0=str(inp0)
+    if sinp0 in seen:
+        #print("already seen!")
+        return 0
+    seen[sinp0]=1
+    out=gen(inp0)
+    for inp in reversed(out):
+        #print(f"step={step} walking inp={inp} seen={seen}")
+        #print(f"step={step} walking inp={inp} seen={len(seen)}")
+        res=idfs_walk(inp, goal, seen, depth, step+1)
+        if res>0:
+            #print(f"child found returned res={res}")
+            return res
+        #print("first try failed")
+        #0/0
+    #0/0
+    return 0
+
+def idfs(inp0:list, goal:list)->int:
+    depth=0
+    res=0
+    print()
+    while True:
+        seen={}
+        res = idfs_walk(inp0, goal, seen, depth)
+        if res>0:
+            #print(f"found res={res} at depth={depth}")
+            break
+        depth+=1
+    return res
+
+class T000(unittest.TestCase):
+    def test_idfs_0000(self):
+        init=[[0,2,3],[1,4,5],[8,7,6]]
+        goal=[[1,2,3],[4,5,6],[8,7,0]]
+        res=idfs(init, goal)
+        self.assertEqual(4, res)
+    def test_dfs_0004(self):
+        init=[[0,2,3],[1,4,5],[8,7,6]]
+        goal=[[1,2,3],[8,0,4],[7,6,5]]
+        res=dfs(init, goal)
+        self.assertEqual(32, res)
+    def test_dfs_0003(self):
+        init=[[0,2,3],[1,4,5],[8,7,6]]
+        goal=[[1,2,3],[8,4,5],[7,0,6]]
+        res=dfs(init, goal)
+        self.assertEqual(3, res)
+    def test_dfs_0002(self):
+        init=[[0,2,3],[1,4,5],[8,7,6]]
+        goal=[[1,2,3],[8,4,5],[0,7,6]]
+        res=dfs(init, goal)
+        self.assertEqual(2, res)
+    def test_dfs_0001(self):
+        init=[[0,2,3],[1,4,5],[8,7,6]]
+        goal=[[1,2,3],[0,4,5],[8,7,6]]
+        res=dfs(init, goal)
+        self.assertEqual(1, res)
+    def test_dfs_0000(self):
+        init=[[0,2,3],[1,4,5],[8,7,6]]
+        goal=[[0,2,3],[1,4,5],[8,7,6]]
+        res=dfs(init, goal)
+        self.assertEqual(0, res)
+    def test_0000(self):
+        #print()
+        inp,out,last=[],[],None
+        # initial input as previous output
+        out+=[[ [[0,2,3],[1,4,5],[8,7,6]]]]
+        # expected output reference
+        outr=[  [[2,0,3],[1,4,5],[8,7,6]],
+                [[1,2,3],[0,4,5],[8,7,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+
+        outr=[  [[1,2,3],[4,0,5],[8,7,6]],
+                [[0,2,3],[1,4,5],[8,7,6]],
+                [[1,2,3],[8,4,5],[0,7,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+        self.assertEqual(out[0][0],out[2][1])
+
+        outr=[  [[1,2,3],[8,4,5],[7,0,6]],
+                [[1,2,3],[0,4,5],[8,7,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+        self.assertEqual(out[1][1],out[3][1])
+
+        outr=[  [[1,2,3],[8,4,5],[0,7,6]],
+                [[1,2,3],[8,4,5],[7,6,0]],
+                [[1,2,3],[8,0,5],[7,4,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+
+        outr=[  [[1,2,3],[0,8,5],[7,4,6]],
+                [[1,2,3],[8,5,0],[7,4,6]],
+                [[1,0,3],[8,2,5],[7,4,6]],
+                [[1,2,3],[8,4,5],[7,0,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+        self.assertEqual(out[3][0],out[5][3])
+
+        outr=[  [[0,1,3],[8,2,5],[7,4,6]],
+                [[1,3,0],[8,2,5],[7,4,6]],
+                [[1,2,3],[8,0,5],[7,4,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+        self.assertEqual(out[4][2],out[6][2])
+
+        outr=[  [[1,0,3],[8,2,5],[7,4,6]],
+                [[1,3,5],[8,2,0],[7,4,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+
+        outr=[  [[1,3,5],[8,0,2],[7,4,6]],
+                [[1,3,0],[8,2,5],[7,4,6]],
+                [[1,3,5],[8,2,6],[7,4,0]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])
+
+        outr=[  [[1,3,5],[8,2,6],[7,0,4]],
+                [[1,3,5],[8,2,0],[7,4,6]],]
+        inp+=[get_next(out[-1],last)];last=inp[-2]if len(inp)>1 else[]
+        out+=[gen(inp[-1])];disp_valid(out[-1],last)
+        self.assertEqual(outr,out[-1])