move tests to test/backend (#14691)

* move tests to test/backend

* fix imports

* fix CI

* revert that one

* Fix formatting in README for test command

test/backend/test_kernel_cache.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+import unittest
+from tinygrad.tensor import Tensor
+from tinygrad import Device
+
+class TestKernelCache(unittest.TestCase):
+  def test_kernel_cache_in_action(self):
+    if Device.DEFAULT not in ["CPU"]:
+      self.skipTest("No custom kernel cache is implemented")
+
+    unique_const = 0.6765677269
+    a = Tensor.rand(4,4).realize()
+    b = Tensor.rand(4,4).realize()
+    x = a + b + unique_const
+    x.realize()
+
+    a1 = Tensor.rand(4,4).realize()
+    b1 = Tensor.rand(4,4).realize()
+    orig_compile_func = Device['CPU'].compiler.compile_cached
+    Device['CPU'].compiler.compile_cached = None # making it not callable
+
+    try:
+      x1 = a1 + b1 + unique_const
+      x1.realize() # Same kernel should be from cache.
+    finally:
+      Device['CPU'].compiler.compile_cached = orig_compile_func
+
+if __name__ == "__main__":
+  unittest.main()