diff --git a/test/test_jit_cases.py b/test/test_jit_cases.py
new file mode 100644
index 0000000000..dd474e3532
--- /dev/null
+++ b/test/test_jit_cases.py
@@ -0,0 +1,78 @@
+import unittest
+from tinygrad import TinyJit, Tensor
+
+# The JIT functions as a "capturing" JIT.
+# Whatever kernels ran in the JIT the second run through the function will be the kernels that will run from then on.
+# Explicit inputs to the function are updated in the JIT graph to the new inputs.
+
+# JITs have four tensor types
+#  1. Tensors that are explicit in the input, aka what's passed in. TODO: support lists/dicts/classes, anything get_state works on
+#  2. Tensors that are explicit in the output, aka what's returned. TODO: same as above
+#  3. Tensors that are implicit in the input as a closure.
+#  4. Tensors that are implicit in the output because they were assigned to and realized.
+
+# explicit inputs and outputs are realized on their way in and out of the JIT
+# there's a whole bunch of edge cases and weirdness here that needs to be tested and clarified.
+
+class TestJitCases(unittest.TestCase):
+  def test_explicit(self):
+    # this function has an explicit input and an explicit output
+    @TinyJit
+    def f(x:Tensor):
+      ret:Tensor = x*2
+      return ret
+
+    for i in range(5):
+      out = f(Tensor([i]))
+      self.assertEqual(out.item(), i*2)
+
+  def test_implicit_input(self):
+    # x is the implicit input (like a weight)
+    x = Tensor([0])
+
+    # this function has an implicit input and an explicit output
+    @TinyJit
+    def f():
+      ret:Tensor = x*2
+      return ret
+
+    for i in range(5):
+      # NOTE: this must be realized here, otherwise the update doesn't happen
+      # if we were explicitly tracking the implicit input Tensors, we might not need this realize
+      x.assign(Tensor([i])).realize()
+      out = f()
+      self.assertEqual(out.item(), i*2)
+
+  def test_implicit_output(self):
+    # out is the implicit output (it's assigned to)
+    out = Tensor([0])
+
+    # this function has an explicit input and an implicit output
+    @TinyJit
+    def f(x:Tensor):
+      # NOTE: this must be realized here
+      # if we were explicitly tracking the implicit output Tensors, we might not need this realize
+      out.assign(x*2).realize()
+
+    for i in range(5):
+      f(Tensor([i]))
+      self.assertEqual(out.item(), i*2)
+
+  def test_implicit_io(self):
+    # x is the implicit input (like a weight)
+    # out is the implicit output (it's assigned to)
+    x = Tensor([0])
+    out = Tensor([0])
+
+    # this function has an implicit input and an implicit output
+    @TinyJit
+    def f():
+      out.assign(x*2).realize() # NOTE: this must be realized here
+
+    for i in range(5):
+      x.assign(Tensor([i])).realize()
+      f()
+      self.assertEqual(out.item(), i*2)
+
+if __name__ == '__main__':
+  unittest.main()