diff --git a/src/main/kotlin/function/builtin/special/AND.java b/src/main/kotlin/function/builtin/special/AND.java
deleted file mode 100644
index 7f299f5..0000000
--- a/src/main/kotlin/function/builtin/special/AND.java
+++ /dev/null
@@ -1,43 +0,0 @@
-package function.builtin.special;
-
-import function.ArgumentValidator;
-import function.FunctionNames;
-import function.LispSpecialFunction;
-import recursion.TailCall;
-import sexpression.Cons;
-import sexpression.SExpression;
-import sexpression.Symbol;
-
-import static function.builtin.Eval.eval;
-import static recursion.TailCalls.done;
-import static recursion.TailCalls.tailCall;
-
-@FunctionNames({ "AND" })
-public class AND extends LispSpecialFunction {
-
-    private ArgumentValidator argumentValidator;
-
-    public AND(String name) {
-        this.argumentValidator = new ArgumentValidator(name);
-    }
-
-    @Override
-    public SExpression call(Cons argumentList) {
-        argumentValidator.validate(argumentList);
-
-        return callTailRecursive(argumentList, Symbol.Companion.getT()).invoke();
-    }
-
-    private TailCall<SExpression> callTailRecursive(Cons argumentList, SExpression lastValue) {
-        SExpression currentValue = eval(argumentList.getFirst());
-        Cons remainingValues = (Cons) argumentList.getRest();
-
-        if (argumentList.isNull())
-            return done(lastValue);
-
-        if (currentValue.isNull())
-            return done(currentValue);
-
-        return tailCall(() -> callTailRecursive(remainingValues, currentValue));
-    }
-}
diff --git a/src/main/kotlin/function/builtin/special/And.kt b/src/main/kotlin/function/builtin/special/And.kt
new file mode 100644
index 0000000..9f173c6
--- /dev/null
+++ b/src/main/kotlin/function/builtin/special/And.kt
@@ -0,0 +1,32 @@
+package function.builtin.special
+
+import function.ArgumentValidator
+import function.FunctionNames
+import function.LispSpecialFunction
+import function.builtin.Eval.Companion.eval
+import sexpression.Cons
+import sexpression.SExpression
+import sexpression.Symbol.Companion.T
+
+@FunctionNames("AND")
+class And(name: String) : LispSpecialFunction() {
+
+    private val argumentValidator = ArgumentValidator(name)
+
+    override fun call(argumentList: Cons): SExpression {
+        argumentValidator.validate(argumentList)
+
+        return callTailRecursive(argumentList, T)
+    }
+
+    private tailrec fun callTailRecursive(argumentList: Cons, lastValue: SExpression): SExpression {
+        val currentValue = eval(argumentList.first)
+        val remainingValues = argumentList.rest as Cons
+
+        return when {
+            argumentList.isNull -> lastValue
+            currentValue.isNull -> currentValue
+            else                -> callTailRecursive(remainingValues, currentValue)
+        }
+    }
+}
diff --git a/src/main/kotlin/function/builtin/special/OR.java b/src/main/kotlin/function/builtin/special/OR.java
deleted file mode 100644
index ba310bc..0000000
--- a/src/main/kotlin/function/builtin/special/OR.java
+++ /dev/null
@@ -1,39 +0,0 @@
-package function.builtin.special;
-
-import function.ArgumentValidator;
-import function.FunctionNames;
-import function.LispSpecialFunction;
-import recursion.TailCall;
-import sexpression.Cons;
-import sexpression.SExpression;
-
-import static function.builtin.Eval.eval;
-import static recursion.TailCalls.done;
-import static recursion.TailCalls.tailCall;
-
-@FunctionNames({ "OR" })
-public class OR extends LispSpecialFunction {
-
-    private ArgumentValidator argumentValidator;
-
-    public OR(String name) {
-        this.argumentValidator = new ArgumentValidator(name);
-    }
-
-    @Override
-    public SExpression call(Cons argumentList) {
-        argumentValidator.validate(argumentList);
-
-        return callTailRecursive(argumentList).invoke();
-    }
-
-    private TailCall<SExpression> callTailRecursive(Cons argumentList) {
-        SExpression currentValue = eval(argumentList.getFirst());
-        Cons remainingValues = (Cons) argumentList.getRest();
-
-        if (remainingValues.isNull() || !currentValue.isNull())
-            return done(currentValue);
-
-        return tailCall(() -> callTailRecursive(remainingValues));
-    }
-}
diff --git a/src/main/kotlin/function/builtin/special/Or.kt b/src/main/kotlin/function/builtin/special/Or.kt
new file mode 100644
index 0000000..cca2eed
--- /dev/null
+++ b/src/main/kotlin/function/builtin/special/Or.kt
@@ -0,0 +1,30 @@
+package function.builtin.special
+
+import function.ArgumentValidator
+import function.FunctionNames
+import function.LispSpecialFunction
+import function.builtin.Eval.Companion.eval
+import sexpression.Cons
+import sexpression.SExpression
+
+@FunctionNames("OR")
+class Or(name: String) : LispSpecialFunction() {
+
+    private val argumentValidator = ArgumentValidator(name)
+
+    override fun call(argumentList: Cons): SExpression {
+        argumentValidator.validate(argumentList)
+
+        return callTailRecursive(argumentList)
+    }
+
+    private tailrec fun callTailRecursive(argumentList: Cons): SExpression {
+        val currentValue = eval(argumentList.first)
+        val remainingValues = argumentList.rest as Cons
+
+        return if (remainingValues.isNull || !currentValue.isNull)
+            currentValue
+        else
+            callTailRecursive(remainingValues)
+    }
+}
diff --git a/src/test/kotlin/function/builtin/special/ANDTest.java b/src/test/kotlin/function/builtin/special/ANDTest.java
deleted file mode 100644
index 0ec6c14..0000000
--- a/src/test/kotlin/function/builtin/special/ANDTest.java
+++ /dev/null
@@ -1,64 +0,0 @@
-package function.builtin.special;
-
-import function.builtin.Eval.UndefinedSymbolException;
-import org.junit.Test;
-import sexpression.LispNumber;
-import testutil.SymbolAndFunctionCleaner;
-
-import static testutil.TestUtilities.assertSExpressionsMatch;
-import static testutil.TestUtilities.evaluateString;
-import static testutil.TypeAssertions.assertNil;
-import static testutil.TypeAssertions.assertT;
-
-public class ANDTest extends SymbolAndFunctionCleaner {
-
-    @Test
-    public void andByItself() {
-        String input = "(and)";
-
-        assertT(evaluateString(input));
-    }
-
-    @Test
-    public void andWithNil() {
-        String input = "(and nil)";
-
-        assertNil(evaluateString(input));
-    }
-
-    @Test
-    public void andWithT() {
-        String input = "(and t)";
-
-        assertT(evaluateString(input));
-    }
-
-    @Test
-    public void andWithNumber() {
-        String input = "(and 7)";
-
-        assertSExpressionsMatch(new LispNumber("7"), evaluateString(input));
-    }
-
-    @Test
-    public void andWithSeveralValues() {
-        String input = "(and t t nil t t)";
-
-        assertNil(evaluateString(input));
-    }
-
-    @Test
-    public void andWithSeveralNumbers() {
-        String input = "(and 1 2 3)";
-
-        assertSExpressionsMatch(new LispNumber("3"), evaluateString(input));
-    }
-
-    @Test(expected = UndefinedSymbolException.class)
-    public void andShortCircuits() {
-        String input = "(and nil (setq x 22))";
-
-        assertNil(evaluateString(input));
-        evaluateString("x");
-    }
-}
diff --git a/src/test/kotlin/function/builtin/special/AndTest.kt b/src/test/kotlin/function/builtin/special/AndTest.kt
new file mode 100644
index 0000000..1909c43
--- /dev/null
+++ b/src/test/kotlin/function/builtin/special/AndTest.kt
@@ -0,0 +1,69 @@
+package function.builtin.special
+
+import function.builtin.Eval.UndefinedSymbolException
+import org.junit.jupiter.api.Assertions.assertThrows
+import org.junit.jupiter.api.Test
+import sexpression.LispNumber
+import testutil.LispTestInstance
+import testutil.SymbolAndFunctionCleaner
+import testutil.TestUtilities.assertSExpressionsMatch
+import testutil.TestUtilities.evaluateString
+import testutil.TypeAssertions.assertNil
+import testutil.TypeAssertions.assertT
+
+@LispTestInstance
+class AndTest : SymbolAndFunctionCleaner() {
+
+    @Test
+    fun andByItself() {
+        val input = "(and)"
+
+        assertT(evaluateString(input))
+    }
+
+    @Test
+    fun andWithNil() {
+        val input = "(and nil)"
+
+        assertNil(evaluateString(input))
+    }
+
+    @Test
+    fun andWithT() {
+        val input = "(and t)"
+
+        assertT(evaluateString(input))
+    }
+
+    @Test
+    fun andWithNumber() {
+        val input = "(and 7)"
+
+        assertSExpressionsMatch(LispNumber("7"), evaluateString(input))
+    }
+
+    @Test
+    fun andWithSeveralValues() {
+        val input = "(and t t nil t t)"
+
+        assertNil(evaluateString(input))
+    }
+
+    @Test
+    fun andWithSeveralNumbers() {
+        val input = "(and 1 2 3)"
+
+        assertSExpressionsMatch(LispNumber("3"), evaluateString(input))
+    }
+
+    @Test
+    fun andShortCircuits() {
+        val input = "(and nil (setq x 22))"
+
+        assertNil(evaluateString(input))
+
+        assertThrows(UndefinedSymbolException::class.java) {
+            evaluateString("x")
+        }
+    }
+}
diff --git a/src/test/kotlin/function/builtin/special/LambdaTest.kt b/src/test/kotlin/function/builtin/special/LambdaTest.kt
index 6409dbe..244b6a3 100644
--- a/src/test/kotlin/function/builtin/special/LambdaTest.kt
+++ b/src/test/kotlin/function/builtin/special/LambdaTest.kt
@@ -16,11 +16,13 @@ import sexpression.LispNumber.Companion.ONE
 import sexpression.Nil
 import sexpression.Symbol
 import sexpression.Symbol.Companion.T
+import testutil.LispTestInstance
 import testutil.SymbolAndFunctionCleaner
 import testutil.TestUtilities.assertSExpressionsMatch
 import testutil.TestUtilities.evaluateString
 import testutil.TestUtilities.parseString
 
+@LispTestInstance
 class LambdaTest : SymbolAndFunctionCleaner() {
 
     @Test
diff --git a/src/test/kotlin/function/builtin/special/ORTest.java b/src/test/kotlin/function/builtin/special/ORTest.java
deleted file mode 100644
index cc9006d..0000000
--- a/src/test/kotlin/function/builtin/special/ORTest.java
+++ /dev/null
@@ -1,64 +0,0 @@
-package function.builtin.special;
-
-import function.builtin.Eval.UndefinedSymbolException;
-import org.junit.Test;
-import sexpression.LispNumber;
-import testutil.SymbolAndFunctionCleaner;
-
-import static testutil.TestUtilities.assertSExpressionsMatch;
-import static testutil.TestUtilities.evaluateString;
-import static testutil.TypeAssertions.assertNil;
-import static testutil.TypeAssertions.assertT;
-
-public class ORTest extends SymbolAndFunctionCleaner {
-
-    @Test
-    public void orByItself() {
-        String input = "(or)";
-
-        assertNil(evaluateString(input));
-    }
-
-    @Test
-    public void orWithNil() {
-        String input = "(or nil)";
-
-        assertNil(evaluateString(input));
-    }
-
-    @Test
-    public void orWithT() {
-        String input = "(or t)";
-
-        assertT(evaluateString(input));
-    }
-
-    @Test
-    public void orWithNumber() {
-        String input = "(or 7)";
-
-        assertSExpressionsMatch(new LispNumber("7"), evaluateString(input));
-    }
-
-    @Test
-    public void orWithSeveralValues() {
-        String input = "(or nil nil nil t nil)";
-
-        assertT(evaluateString(input));
-    }
-
-    @Test
-    public void orWithSeveralNumbers() {
-        String input = "(or 1 2 3)";
-
-        assertSExpressionsMatch(new LispNumber("1"), evaluateString(input));
-    }
-
-    @Test(expected = UndefinedSymbolException.class)
-    public void orShortCircuits() {
-        String input = "(or t (setq x 22))";
-
-        assertT(evaluateString(input));
-        evaluateString("x");
-    }
-}
diff --git a/src/test/kotlin/function/builtin/special/OrTest.kt b/src/test/kotlin/function/builtin/special/OrTest.kt
new file mode 100644
index 0000000..2cd48e2
--- /dev/null
+++ b/src/test/kotlin/function/builtin/special/OrTest.kt
@@ -0,0 +1,69 @@
+package function.builtin.special
+
+import function.builtin.Eval.UndefinedSymbolException
+import org.junit.jupiter.api.Assertions.assertThrows
+import org.junit.jupiter.api.Test
+import sexpression.LispNumber
+import testutil.LispTestInstance
+import testutil.SymbolAndFunctionCleaner
+import testutil.TestUtilities.assertSExpressionsMatch
+import testutil.TestUtilities.evaluateString
+import testutil.TypeAssertions.assertNil
+import testutil.TypeAssertions.assertT
+
+@LispTestInstance
+class OrTest : SymbolAndFunctionCleaner() {
+
+    @Test
+    fun orByItself() {
+        val input = "(or)"
+
+        assertNil(evaluateString(input))
+    }
+
+    @Test
+    fun orWithNil() {
+        val input = "(or nil)"
+
+        assertNil(evaluateString(input))
+    }
+
+    @Test
+    fun orWithT() {
+        val input = "(or t)"
+
+        assertT(evaluateString(input))
+    }
+
+    @Test
+    fun orWithNumber() {
+        val input = "(or 7)"
+
+        assertSExpressionsMatch(LispNumber("7"), evaluateString(input))
+    }
+
+    @Test
+    fun orWithSeveralValues() {
+        val input = "(or nil nil nil t nil)"
+
+        assertT(evaluateString(input))
+    }
+
+    @Test
+    fun orWithSeveralNumbers() {
+        val input = "(or 1 2 3)"
+
+        assertSExpressionsMatch(LispNumber("1"), evaluateString(input))
+    }
+
+    @Test
+    fun orShortCircuits() {
+        val input = "(or t (setq x 22))"
+
+        assertT(evaluateString(input))
+
+        assertThrows(UndefinedSymbolException::class.java) {
+            evaluateString("x")
+        }
+    }
+}
diff --git a/src/test/kotlin/function/builtin/special/SetqTest.java b/src/test/kotlin/function/builtin/special/SetqTest.java
deleted file mode 100644
index 1e5a152..0000000
--- a/src/test/kotlin/function/builtin/special/SetqTest.java
+++ /dev/null
@@ -1,94 +0,0 @@
-package function.builtin.special;
-
-import function.ArgumentValidator.BadArgumentTypeException;
-import function.ArgumentValidator.TooFewArgumentsException;
-import function.ArgumentValidator.TooManyArgumentsException;
-import function.builtin.Eval.UndefinedSymbolException;
-import org.junit.Test;
-import sexpression.LispNumber;
-import table.SymbolTable;
-import testutil.SymbolAndFunctionCleaner;
-
-import static org.junit.Assert.assertNull;
-import static testutil.TestUtilities.assertSExpressionsMatch;
-import static testutil.TestUtilities.evaluateString;
-
-public class SetqTest extends SymbolAndFunctionCleaner {
-
-    @Test
-    public void setq() {
-        evaluateString("(setq a 23)");
-        assertSExpressionsMatch(new LispNumber("23"), evaluateString("a"));
-    }
-
-    @Test
-    public void lookupDefinedSymbol() {
-        evaluateString("(setq a 23)");
-        assertSExpressionsMatch(new LispNumber("23"), getExecutionContext().lookupSymbolValue("A"));
-    }
-
-    @Test
-    public void lookupUndefinedSymbol() {
-        assertNull(getExecutionContext().lookupSymbolValue("A"));
-    }
-
-    @Test
-    public void setqGlobalVariable() {
-        evaluateString("(setq a 23)");
-        SymbolTable global = getExecutionContext().getScope();
-        getExecutionContext().setScope(new SymbolTable(global));
-
-        evaluateString("(setq a 94)");
-        getExecutionContext().setScope(global);
-        assertSExpressionsMatch(new LispNumber("94"), evaluateString("a"));
-    }
-
-    @Test
-    public void setqLocalVariable() {
-        SymbolTable global = getExecutionContext().getScope();
-        SymbolTable local = new SymbolTable(global);
-        local.set("A", new LispNumber("99"));
-        getExecutionContext().setScope(local);
-
-        evaluateString("(setq a 94)");
-        assertSExpressionsMatch(new LispNumber("94"), evaluateString("a"));
-    }
-
-    @Test(expected = UndefinedSymbolException.class)
-    public void setqLocalVariableDefined_DoesNotSetGlobal() {
-        SymbolTable global = getExecutionContext().getScope();
-        SymbolTable local = new SymbolTable(global);
-        local.set("A", new LispNumber("99"));
-        getExecutionContext().setScope(local);
-
-        evaluateString("(setq a 94)");
-        getExecutionContext().setScope(global);
-        evaluateString("a");
-    }
-
-    @Test
-    public void setqLocalVariableUndefined_SetsGlobal() {
-        SymbolTable global = getExecutionContext().getScope();
-        SymbolTable local = new SymbolTable(global);
-        getExecutionContext().setScope(local);
-
-        evaluateString("(setq a 94)");
-        getExecutionContext().setScope(global);
-        assertSExpressionsMatch(new LispNumber("94"), evaluateString("a"));
-    }
-
-    @Test(expected = BadArgumentTypeException.class)
-    public void setqWithNonSymbol() {
-        evaluateString("(setq 1 2)");
-    }
-
-    @Test(expected = TooFewArgumentsException.class)
-    public void setqWithTooFewArguments() {
-        evaluateString("(setq x)");
-    }
-
-    @Test(expected = TooManyArgumentsException.class)
-    public void setqWithTooManyArguments() {
-        evaluateString("(setq a b c)");
-    }
-}
diff --git a/src/test/kotlin/function/builtin/special/SetqTest.kt b/src/test/kotlin/function/builtin/special/SetqTest.kt
new file mode 100644
index 0000000..d590efc
--- /dev/null
+++ b/src/test/kotlin/function/builtin/special/SetqTest.kt
@@ -0,0 +1,105 @@
+package function.builtin.special
+
+import function.ArgumentValidator.BadArgumentTypeException
+import function.ArgumentValidator.TooFewArgumentsException
+import function.ArgumentValidator.TooManyArgumentsException
+import function.builtin.Eval.UndefinedSymbolException
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Assertions.assertThrows
+import org.junit.jupiter.api.Test
+import sexpression.LispNumber
+import table.SymbolTable
+import testutil.LispTestInstance
+import testutil.SymbolAndFunctionCleaner
+import testutil.TestUtilities.assertSExpressionsMatch
+import testutil.TestUtilities.evaluateString
+
+@LispTestInstance
+class SetqTest : SymbolAndFunctionCleaner() {
+
+    @Test
+    fun setq() {
+        evaluateString("(setq a 23)")
+        assertSExpressionsMatch(LispNumber("23"), evaluateString("a"))
+    }
+
+    @Test
+    fun lookupDefinedSymbol() {
+        evaluateString("(setq a 23)")
+        assertSExpressionsMatch(LispNumber("23"), executionContext.lookupSymbolValue("A")!!)
+    }
+
+    @Test
+    fun lookupUndefinedSymbol() {
+        assertThat(executionContext.lookupSymbolValue("A")).isNull()
+    }
+
+    @Test
+    fun setqGlobalVariable() {
+        evaluateString("(setq a 23)")
+        val global = executionContext.scope
+        executionContext.scope = SymbolTable(global)
+
+        evaluateString("(setq a 94)")
+        executionContext.scope = global
+        assertSExpressionsMatch(LispNumber("94"), evaluateString("a"))
+    }
+
+    @Test
+    fun setqLocalVariable() {
+        val global = executionContext.scope
+        val local = SymbolTable(global)
+        local["A"] = LispNumber("99")
+        executionContext.scope = local
+
+        evaluateString("(setq a 94)")
+        assertSExpressionsMatch(LispNumber("94"), evaluateString("a"))
+    }
+
+    @Test
+    fun setqLocalVariableDefined_DoesNotSetGlobal() {
+        val global = executionContext.scope
+        val local = SymbolTable(global)
+        local["A"] = LispNumber("99")
+        executionContext.scope = local
+
+        evaluateString("(setq a 94)")
+        executionContext.scope = global
+
+        assertThrows(UndefinedSymbolException::class.java) {
+            evaluateString("a")
+        }
+    }
+
+    @Test
+    fun setqLocalVariableUndefined_SetsGlobal() {
+        val global = executionContext.scope
+        val local = SymbolTable(global)
+        executionContext.scope = local
+
+        evaluateString("(setq a 94)")
+        executionContext.scope = global
+        assertSExpressionsMatch(LispNumber("94"), evaluateString("a"))
+    }
+
+    @Test
+    fun setqWithNonSymbol() {
+        assertThrows(BadArgumentTypeException::class.java) {
+            evaluateString("(setq 1 2)")
+        }
+    }
+
+    @Test
+    fun setqWithTooFewArguments() {
+        assertThrows(TooFewArgumentsException::class.java) {
+            evaluateString("(setq x)")
+        }
+    }
+
+    @Test
+    fun setqWithTooManyArguments() {
+        assertThrows(TooManyArgumentsException::class.java) {
+            evaluateString("(setq a b c)")
+        }
+    }
+}