diff --git a/tests/test_eval.py b/tests/test_eval.py
index f9046a4..10d3da3 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -40,3 +40,51 @@ def test_eval():
     ob = RestrictionCapableEval(exp)
     ret = ob.eval({'m': [1, 2]})
     assert ret == [2, 1]
+
+
+def test_Eval__RestrictionCapableEval_1():
+    """It raises SyntaxError when there are errors
+    (by using forbidden stuff) in the code."""
+    ob = RestrictionCapableEval("_a")
+    with pytest.raises(SyntaxError):
+        ob.prepRestrictedCode()
+
+
+def test_Eval__RestictionCapableEval__prepUnrestrictedCode_1():
+    """It does nothing when unrestricted code is already set by init."""
+    ob = RestrictionCapableEval("a")
+    assert ob.used == ('a',)
+    ob.expr = "b"
+    ob.prepUnrestrictedCode()
+    assert ob.used == ('a',)
+
+
+def test_Eval__RestictionCapableEval__prepUnrestrictedCode_2():
+    """It does not re-set 'used' if it is already set by an earlier call."""
+    ob = RestrictionCapableEval("a")
+    assert ob.used == ('a',)
+    ob.used = ('b',)
+    # This is needed to force re-compilation
+    ob.ucode = None
+    ob.prepUnrestrictedCode()
+    # If it was called again, used would be ('a',) again.
+    assert ob.used == ('b',)
+
+
+def test_Eval__RestictionCapableEval__prepRestrictedCode_1():
+    """It does nothing when restricted code is already set by prepRestrictedCode."""
+    ob = RestrictionCapableEval("a")
+    ob.prepRestrictedCode()
+    assert ob.used == ('a',)
+    ob.expr = "b"
+    ob.prepRestrictedCode()
+    assert ob.used == ('a',)
+
+
+def test_Eval__RestictionCapableEval__eval_1():
+    """It does not add names from the mapping to the
+    global scope which are already there."""
+    ob = RestrictionCapableEval("a + b + c")
+    ob.globals['c'] = 8
+    result = ob.eval(dict(a=1, b=2, c=4))
+    assert result == 11