diff --git a/simple_test/fixtures/ast/binary.ast b/simple_test/fixtures/ast/binary.ast
new file mode 100644
index 0000000..96976a2
--- /dev/null
+++ b/simple_test/fixtures/ast/binary.ast
@@ -0,0 +1,18 @@
+instructions =>
+  Write:
+  expression =>
+    Binary (DIV):
+    left =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
+    right =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
diff --git a/simple_test/fixtures/ast/binary.sim b/simple_test/fixtures/ast/binary.sim
new file mode 100644
index 0000000..570808d
--- /dev/null
+++ b/simple_test/fixtures/ast/binary.sim
@@ -0,0 +1,5 @@
+PROGRAM x;
+  VAR a,b: INTEGER;
+BEGIN
+  WRITE a DIV b
+END x.
diff --git a/simple_test/fixtures/ast/binary1.ast b/simple_test/fixtures/ast/binary1.ast
new file mode 100644
index 0000000..1afb2fc
--- /dev/null
+++ b/simple_test/fixtures/ast/binary1.ast
@@ -0,0 +1,26 @@
+instructions =>
+  Assign:
+  location =>
+    Variable:
+    variable =>
+      VAR BEGIN
+        type:
+          ARRAY BEGIN
+            type:
+              INTEGER
+            length:
+              5
+          END ARRAY
+      END VAR
+  expression =>
+    Variable:
+    variable =>
+      VAR BEGIN
+        type:
+          ARRAY BEGIN
+            type:
+              INTEGER
+            length:
+              5
+          END ARRAY
+      END VAR
diff --git a/simple_test/fixtures/ast/binary1.sim b/simple_test/fixtures/ast/binary1.sim
new file mode 100644
index 0000000..5c7bfe8
--- /dev/null
+++ b/simple_test/fixtures/ast/binary1.sim
@@ -0,0 +1,5 @@
+PROGRAM x;
+    VAR a,b: ARRAY 5 OF INTEGER;
+BEGIN
+    a := b
+END x.
diff --git a/simple_test/fixtures/ast/binary2.sim b/simple_test/fixtures/ast/binary2.sim
new file mode 100644
index 0000000..5617500
--- /dev/null
+++ b/simple_test/fixtures/ast/binary2.sim
@@ -0,0 +1,6 @@
+PROGRAM x;
+    VAR a: ARRAY 5 OF INTEGER;
+    VAR b: ARRAY 5 OF INTEGER;
+BEGIN
+    a := b
+END x.
diff --git a/simple_test/fixtures/ast/div.ast b/simple_test/fixtures/ast/div.ast
new file mode 100644
index 0000000..96976a2
--- /dev/null
+++ b/simple_test/fixtures/ast/div.ast
@@ -0,0 +1,18 @@
+instructions =>
+  Write:
+  expression =>
+    Binary (DIV):
+    left =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
+    right =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
diff --git a/simple_test/fixtures/ast/div.sim b/simple_test/fixtures/ast/div.sim
new file mode 100644
index 0000000..570808d
--- /dev/null
+++ b/simple_test/fixtures/ast/div.sim
@@ -0,0 +1,5 @@
+PROGRAM x;
+  VAR a,b: INTEGER;
+BEGIN
+  WRITE a DIV b
+END x.
diff --git a/simple_test/fixtures/ast/empty.ast b/simple_test/fixtures/ast/empty.ast
new file mode 100644
index 0000000..e69de29
diff --git a/simple_test/fixtures/ast/empty.sim b/simple_test/fixtures/ast/empty.sim
new file mode 100644
index 0000000..aee7d28
--- /dev/null
+++ b/simple_test/fixtures/ast/empty.sim
@@ -0,0 +1 @@
+PROGRAM a; END a.
diff --git a/simple_test/fixtures/ast/if1.ast b/simple_test/fixtures/ast/if1.ast
new file mode 100644
index 0000000..3a704a2
--- /dev/null
+++ b/simple_test/fixtures/ast/if1.ast
@@ -0,0 +1,38 @@
+instructions =>
+  If:
+  condition =>
+    Condition (=):
+    left =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
+    right =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
+  true =>
+    Write:
+    expression =>
+      Variable:
+      variable =>
+        VAR BEGIN
+          type:
+            INTEGER
+        END VAR
+  false =>
+    Write:
+    expression =>
+      Number:
+      value =>
+        CONST BEGIN
+          type:
+            INTEGER
+          value:
+            42
+        END CONST
diff --git a/simple_test/fixtures/ast/if1.sim b/simple_test/fixtures/ast/if1.sim
new file mode 100644
index 0000000..4ef1079
--- /dev/null
+++ b/simple_test/fixtures/ast/if1.sim
@@ -0,0 +1,9 @@
+PROGRAM x;
+  VAR a,b: INTEGER;
+BEGIN
+  IF a = b THEN
+    WRITE a
+  ELSE
+    WRITE 42
+  END
+END x.
diff --git a/simple_test/fixtures/ast/if2.ast b/simple_test/fixtures/ast/if2.ast
new file mode 100644
index 0000000..b25a6b5
--- /dev/null
+++ b/simple_test/fixtures/ast/if2.ast
@@ -0,0 +1,33 @@
+instructions =>
+  If:
+  condition =>
+    Condition (=):
+    left =>
+      Number:
+      value =>
+        CONST BEGIN
+          type:
+            INTEGER
+          value:
+            0
+        END CONST
+    right =>
+      Number:
+      value =>
+        CONST BEGIN
+          type:
+            INTEGER
+          value:
+            0
+        END CONST
+  true =>
+    Write:
+    expression =>
+      Number:
+      value =>
+        CONST BEGIN
+          type:
+            INTEGER
+          value:
+            10
+        END CONST
diff --git a/simple_test/fixtures/ast/if2.sim b/simple_test/fixtures/ast/if2.sim
new file mode 100644
index 0000000..2e1a182
--- /dev/null
+++ b/simple_test/fixtures/ast/if2.sim
@@ -0,0 +1,6 @@
+PROGRAM x;
+BEGIN
+  IF 0 = 0 THEN
+    WRITE 10
+  END
+END x.
diff --git a/simple_test/fixtures/ast/modErr.sim b/simple_test/fixtures/ast/modErr.sim
new file mode 100644
index 0000000..3925b45
--- /dev/null
+++ b/simple_test/fixtures/ast/modErr.sim
@@ -0,0 +1,3 @@
+PROGRAM peter;
+  VAR a : ARRAY 10 DIV (1 - 1) OF INTEGER;
+END peter.
diff --git a/simple_test/fixtures/ast/random.ast b/simple_test/fixtures/ast/random.ast
new file mode 100644
index 0000000..2342ff0
--- /dev/null
+++ b/simple_test/fixtures/ast/random.ast
@@ -0,0 +1,200 @@
+instructions =>
+  Assign:
+  location =>
+    Variable:
+    variable =>
+      VAR BEGIN
+        type:
+          INTEGER
+      END VAR
+  expression =>
+    Number:
+    value =>
+      CONST BEGIN
+        type:
+          INTEGER
+        value:
+          1
+      END CONST
+  If:
+  condition =>
+    Condition (=):
+    left =>
+      Number:
+      value =>
+        CONST BEGIN
+          type:
+            INTEGER
+          value:
+            0
+        END CONST
+    right =>
+      Number:
+      value =>
+        CONST BEGIN
+          type:
+            INTEGER
+          value:
+            0
+        END CONST
+  true =>
+    Repeat:
+    condition =>
+      Condition (#):
+      left =>
+        Number:
+        value =>
+          CONST BEGIN
+            type:
+              INTEGER
+            value:
+              0
+          END CONST
+      right =>
+        Number:
+        value =>
+          CONST BEGIN
+            type:
+              INTEGER
+            value:
+              0
+          END CONST
+    instructions =>
+      Assign:
+      location =>
+        Variable:
+        variable =>
+          VAR BEGIN
+            type:
+              INTEGER
+          END VAR
+      expression =>
+        Binary (-):
+        left =>
+          Binary (*):
+          left =>
+            Number:
+            value =>
+              CONST BEGIN
+                type:
+                  INTEGER
+                value:
+                  16807
+              END CONST
+          right =>
+            Binary (MOD):
+            left =>
+              Variable:
+              variable =>
+                VAR BEGIN
+                  type:
+                    INTEGER
+                END VAR
+            right =>
+              Number:
+              value =>
+                CONST BEGIN
+                  type:
+                    INTEGER
+                  value:
+                    127773
+                END CONST
+        right =>
+          Binary (*):
+          left =>
+            Number:
+            value =>
+              CONST BEGIN
+                type:
+                  INTEGER
+                value:
+                  2836
+              END CONST
+          right =>
+            Binary (DIV):
+            left =>
+              Variable:
+              variable =>
+                VAR BEGIN
+                  type:
+                    INTEGER
+                END VAR
+            right =>
+              Number:
+              value =>
+                CONST BEGIN
+                  type:
+                    INTEGER
+                  value:
+                    127773
+                END CONST
+      If:
+      condition =>
+        Condition (>):
+        left =>
+          Variable:
+          variable =>
+            VAR BEGIN
+              type:
+                INTEGER
+            END VAR
+        right =>
+          Number:
+          value =>
+            CONST BEGIN
+              type:
+                INTEGER
+              value:
+                0
+            END CONST
+      true =>
+        Assign:
+        location =>
+          Variable:
+          variable =>
+            VAR BEGIN
+              type:
+                INTEGER
+            END VAR
+        expression =>
+          Variable:
+          variable =>
+            VAR BEGIN
+              type:
+                INTEGER
+            END VAR
+      false =>
+        Assign:
+        location =>
+          Variable:
+          variable =>
+            VAR BEGIN
+              type:
+                INTEGER
+            END VAR
+        expression =>
+          Binary (+):
+          left =>
+            Variable:
+            variable =>
+              VAR BEGIN
+                type:
+                  INTEGER
+              END VAR
+          right =>
+            Number:
+            value =>
+              CONST BEGIN
+                type:
+                  INTEGER
+                value:
+                  2147483647
+              END CONST
+      Write:
+      expression =>
+        Variable:
+        variable =>
+          VAR BEGIN
+            type:
+              INTEGER
+          END VAR
diff --git a/simple_test/fixtures/ast/random.sim b/simple_test/fixtures/ast/random.sim
new file mode 100644
index 0000000..b57596d
--- /dev/null
+++ b/simple_test/fixtures/ast/random.sim
@@ -0,0 +1,28 @@
+(* $Id: random.sim 30 2006-02-17 17:39:34Z phf $ *)
+
+PROGRAM Random;
+CONST
+  a = 16807;
+  m = 2147483647;
+  q = m DIV a;
+  r = m MOD a;
+VAR
+  Z: INTEGER; (* seed *)
+  g: INTEGER; (* temporary *)
+BEGIN
+  Z := 1;
+  (* Forever... *)
+  WHILE 0 = 0 DO
+    (* ...make next random number... *)
+    g := a*(Z MOD q) - r*(Z DIV q);
+    IF g > 0 THEN Z := g ELSE Z := g + m END;
+    (* ...and print it. *)
+    WRITE Z
+  END
+END Random.
+
+(*
+  This is an integer version of the random number generator
+  described in Wirth, Reiser: Programming in Oberon, 1992.
+  I guess the original reference is Park and Miller, 1988.
+*)