diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 93bc563..8ab19d8 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -8,6 +8,9 @@ use crate::{
     repr::mlog::*,
 };
 
+#[cfg(test)]
+mod test;
+
 /// Represents the instruction pointer
 #[derive(Clone, Copy, PartialEq, PartialOrd, Ord, Eq, Debug)]
 pub struct Counter(pub usize);
@@ -88,6 +91,7 @@ pub struct ProgramState<R: Rng> {
     pub rng: RefCell<R>,
 
     pub ended: bool,
+    // TODO: add errors array
 }
 
 #[non_exhaustive]
@@ -145,6 +149,7 @@ pub fn run(program: &MindustryProgram, stop_condition: StopCondition) -> HashMap
     let mut steps = 0;
 
     while !stop_condition.should_stop(steps, &state) {
+        println!("{:?}", state);
         let _ = step(&compiled, &mut state);
         steps = steps.saturating_add(1);
     }
@@ -248,6 +253,8 @@ pub fn step(
         _ => unimplemented!(),
     }
 
+    state.counter.inc();
+
     Ok(())
 }
 
diff --git a/src/interpreter/test.rs b/src/interpreter/test.rs
new file mode 100644
index 0000000..ef8abe7
--- /dev/null
+++ b/src/interpreter/test.rs
@@ -0,0 +1,126 @@
+use super::*;
+
+#[test]
+fn test_interpret_operation() {
+    fn run_test(
+        instructions: impl IntoIterator<Item = MindustryOperation>,
+    ) -> HashMap<String, Value> {
+        let program = MindustryProgram::from(instructions.into_iter().collect::<Vec<_>>());
+
+        let end_state = run(&program, StopCondition::End);
+
+        end_state
+    }
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Add,
+            Operand::Integer(1),
+            Operand::Float(2.0)
+        )])
+        .get("x"),
+        Some(&Value::Number(3.0))
+    );
+
+    assert_eq!(
+        run_test([
+            MindustryOperation::Set(String::from("a"), Operand::Integer(2)),
+            MindustryOperation::Operator(
+                String::from("x"),
+                Operator::Add,
+                Operand::Variable(String::from("a")),
+                Operand::Integer(1)
+            )
+        ])
+        .get("x"),
+        Some(&Value::Number(3.0))
+    );
+
+    assert_eq!(
+        run_test([
+            MindustryOperation::Set(String::from("a"), Operand::Float(-1.5)),
+            MindustryOperation::Set(String::from("b"), Operand::Float(0.25)),
+            MindustryOperation::Operator(
+                String::from("x"),
+                Operator::Add,
+                Operand::Variable(String::from("a")),
+                Operand::Variable(String::from("b"))
+            )
+        ])
+        .get("x"),
+        Some(&Value::Number(-1.25))
+    );
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Add,
+            Operand::Integer(7),
+            Operand::String(String::from("2"))
+        )])
+        .get("x"),
+        Some(&Value::Number(8.0)),
+        "7 + \"2\" should equal 8"
+    );
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Add,
+            Operand::Integer(7),
+            Operand::String(String::from(""))
+        )])
+        .get("x"),
+        Some(&Value::Number(8.0)),
+        "7 + \"\" should equal 8"
+    );
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Sub,
+            Operand::Integer(7),
+            Operand::Integer(3)
+        )])
+        .get("x"),
+        Some(&Value::Number(4.0)),
+        "7 - 3 should equal 4"
+    );
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Eq,
+            Operand::Integer(7),
+            Operand::Integer(3)
+        )])
+        .get("x"),
+        Some(&Value::Number(0.0)),
+        "7 == 3 should equal 0"
+    );
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Eq,
+            Operand::Integer(7),
+            Operand::Integer(7)
+        )])
+        .get("x"),
+        Some(&Value::Number(1.0)),
+        "7 == 7 should equal 1"
+    );
+
+    assert_eq!(
+        run_test([MindustryOperation::Operator(
+            String::from("x"),
+            Operator::Neq,
+            Operand::Integer(7),
+            Operand::Integer(3)
+        )])
+        .get("x"),
+        Some(&Value::Number(1.0)),
+        "7 != 3 should equal 1"
+    );
+}