diff --git a/test/checker/if_part_test_is_bool.bolt b/test/checker/if_part_test_is_bool.bolt
new file mode 100644
index 000000000..ee660020a
--- /dev/null
+++ b/test/checker/if_part_test_is_bool.bolt
@@ -0,0 +1,8 @@
+
+@expect_diagnostic 2010
+if 1.
+  True
+
+@expect_diagnostic 2010
+if "a".
+  False
diff --git a/test/checker/instance_arguments_type_classes.bolt.disabled b/test/checker/instance_arguments_type_classes.bolt.disabled
new file mode 100644
index 000000000..39c23789b
--- /dev/null
+++ b/test/checker/instance_arguments_type_classes.bolt.disabled
@@ -0,0 +1,36 @@
+
+# Advanced test for instance arguments as type classses
+# From the paper 'On the Bright Side of Type Classes'
+
+# Representation of the type class
+struct Eq a.
+  equal: a -> a -> Bool
+
+let primBoolEq a b = match (a, b).
+  (True, True) => True
+  (False, False) => True
+  _ => False
+
+# Class Eq default method
+let equal {{ eqT : Eq a }} : {{ Eq a }} -> a -> a -> Bool = eqT.equal
+
+# Instance Eq Bool
+let eqBool : Eq Bool = Eq {
+  equal = primBoolEq
+}
+
+# Instance Eq (List a)
+let primListEq a b = match (a, b).
+  ([], []) => True
+  (_, []) => False
+  ([], _) => False
+  (a :: b, c :: d) => equal a c && primListEq b c
+
+# Instance Eq a => Eq List a
+let listEq : Eq a -> Eq (List a) = Eq {
+  equal = primListEq
+}
+
+ equal True False
+ equal 1 2
+ equal 1 False
diff --git a/test/checker/mutual_recursion_is_odd_is_even.bolt b/test/checker/mutual_recursion_is_odd_is_even.bolt
new file mode 100644
index 000000000..8ddbac8af
--- /dev/null
+++ b/test/checker/mutual_recursion_is_odd_is_even.bolt
@@ -0,0 +1,17 @@
+
+# Mutually recusive functions
+
+let is_odd x.
+  if x == 1.
+    return True
+  else.
+    return is_even (x-1)
+
+let is_even x.
+  if x == 0.
+    return True
+  else.
+    return is_odd (x-1)
+
+@:Bool is_even 1
+
diff --git a/test/checker/nested_vars_reaching_parent_scope.bolt b/test/checker/nested_vars_reaching_parent_scope.bolt
new file mode 100644
index 000000000..602f1a243
--- /dev/null
+++ b/test/checker/nested_vars_reaching_parent_scope.bolt
@@ -0,0 +1,12 @@
+
+# Testing whether nested variable declarations work
+
+let id x.
+  let foo = x
+  return foo
+
+@:Int id 1
+@:Bool id True
+@:Int id 1
+@:String id "foo"
+
diff --git a/test/checker/pattern_matching_variant.bolt b/test/checker/pattern_matching_variant.bolt
new file mode 100644
index 000000000..d1acf88a5
--- /dev/null
+++ b/test/checker/pattern_matching_variant.bolt
@@ -0,0 +1,13 @@
+
+enum MyList a.
+  Nil
+  Pair a (MyList a)
+
+let (Pair True Nil) : MyList Bool
+let (Pair "foo" Nil) : MyList String
+
+@expect_diagnostic 2010
+let (Pair 1 Nil) : MyList Bool
+
+let Nil : MyList a
+
diff --git a/test/checker/simple_instance_arguments.bolt.disabled b/test/checker/simple_instance_arguments.bolt.disabled
new file mode 100644
index 000000000..a0c7962cb
--- /dev/null
+++ b/test/checker/simple_instance_arguments.bolt.disabled
@@ -0,0 +1,10 @@
+
+# Simple test for instance arguments
+
+implicit let theanswer = 1
+
+let is_answer {{ a : Int }} x = a == x
+
+is_answer 1
+is_answer 2
+is_answer 42
diff --git a/test/checker/simple_tuple_test.bolt b/test/checker/simple_tuple_test.bolt
new file mode 100644
index 000000000..6018effee
--- /dev/null
+++ b/test/checker/simple_tuple_test.bolt
@@ -0,0 +1,16 @@
+
+
+let pair x y = (x, y)
+
+let p1 = pair 1 1
+let p2 = (1, True)
+let p3 = (False, 1)
+
+@:Int p1.0
+@:Int p1.1
+
+@:Int p2.0
+@:Bool p2.1
+
+@:Bool p3.0
+@:Int p3.1
diff --git a/test/checker/test_equality_tapp.bolt b/test/checker/test_equality_tapp.bolt
new file mode 100644
index 000000000..d7611b84c
--- /dev/null
+++ b/test/checker/test_equality_tapp.bolt
@@ -0,0 +1,10 @@
+
+enum List a.
+  Nil
+  Pair a (List a)
+
+let x : List Int
+@expect_diagnostic 2010
+let y : List Bool = x
+let z : List String
+
diff --git a/test/checker/test_qualified_type_sigs.bolt b/test/checker/test_qualified_type_sigs.bolt
new file mode 100644
index 000000000..0349492b4
--- /dev/null
+++ b/test/checker/test_qualified_type_sigs.bolt
@@ -0,0 +1,24 @@
+
+
+class Eq a.
+  let eq : a -> a -> Bool
+
+class Show a.
+  let show : a -> String
+
+instance Eq String.
+  let eq a b = True
+
+instance Show Bool.
+  let show s = "a boolean"
+
+instance Show Int.
+  let show s = "a string"
+
+let repr_eq_1 x y : (Show a, Show b) => a -> b -> Bool = eq (show x) (show y)
+
+@expect_diagnostic 2201
+let repr_eq_2 x y : (Show b) => a -> b -> Bool = eq (show x) (show y)
+
+@expect_diagnostic 2201
+let repr_eq_3 x y : a -> b -> Bool = eq (show x) (show y)
diff --git a/test/checker/variable_mistyping.bolt b/test/checker/variable_mistyping.bolt
new file mode 100644
index 000000000..b8757cf35
--- /dev/null
+++ b/test/checker/variable_mistyping.bolt
@@ -0,0 +1,6 @@
+
+# Testing variable typing
+
+@expect_diagnostic 2010
+let a: Int = "foo"
+
diff --git a/test/checker/wrong_return_type.bolt b/test/checker/wrong_return_type.bolt
new file mode 100644
index 000000000..ddfb52b21
--- /dev/null
+++ b/test/checker/wrong_return_type.bolt
@@ -0,0 +1,11 @@
+
+let wrong x.
+  if True.
+    return 1
+  elif False.
+    return 2
+  else.
+    @expect_diagnostic 2010
+    return "foo"
+
+wrong 1