diff --git a/src/main/kotlin/environment/RuntimeEnvironment.java b/src/main/kotlin/environment/RuntimeEnvironment.java
deleted file mode 100644
index a728b64..0000000
--- a/src/main/kotlin/environment/RuntimeEnvironment.java
+++ /dev/null
@@ -1,154 +0,0 @@
-package environment;
-
-import error.ErrorManager;
-
-import java.io.InputStream;
-import java.io.PrintStream;
-import java.util.function.Function;
-
-public class RuntimeEnvironment {
-
-    private static RuntimeEnvironment uniqueInstance = new RuntimeEnvironment();
-
-    public static RuntimeEnvironment getInstance() {
-        return uniqueInstance;
-    }
-
-    private String inputName;
-    private InputStream input;
-    private PrintStream output;
-    private PrintStream errorOutput;
-    private ErrorManager errorManager;
-    private String path;
-    private Runnable terminationFunction;
-    private Runnable errorTerminationFunction;
-    private Function<String, String> promptDecorator;
-    private Function<String, String> valueOutputDecorator;
-    private Function<String, String> warningOutputDecorator;
-    private Function<String, String> errorOutputDecorator;
-    private Function<String, String> criticalOutputDecorator;
-
-    private RuntimeEnvironment() {
-        reset();
-    }
-
-    public void reset() {
-        inputName = null;
-        input = null;
-        output = null;
-        errorOutput = null;
-        errorManager = null;
-        path = null;
-        terminationFunction = null;
-        errorTerminationFunction = null;
-        promptDecorator = null;
-        valueOutputDecorator = null;
-        warningOutputDecorator = null;
-        errorOutputDecorator = null;
-        criticalOutputDecorator = null;
-    }
-
-    public void setInputName(String inputName) {
-        this.inputName = inputName;
-    }
-
-    public void setInput(InputStream input) {
-        this.input = input;
-    }
-
-    public void setOutput(PrintStream output) {
-        this.output = output;
-    }
-
-    public void setErrorOutput(PrintStream errorOutput) {
-        this.errorOutput = errorOutput;
-    }
-
-    public void setErrorManager(ErrorManager errorManager) {
-        this.errorManager = errorManager;
-    }
-
-    public void setPath(String path) {
-        this.path = path;
-    }
-
-    public void setTerminationFunction(Runnable terminationFunction) {
-        this.terminationFunction = terminationFunction;
-    }
-
-    public void setErrorTerminationFunction(Runnable errorTerminationFunction) {
-        this.errorTerminationFunction = errorTerminationFunction;
-    }
-
-    public void setPromptDecorator(Function<String, String> promptDecorator) {
-        this.promptDecorator = promptDecorator;
-    }
-
-    public void setValueOutputDecorator(Function<String, String> valueOutputDecorator) {
-        this.valueOutputDecorator = valueOutputDecorator;
-    }
-
-    public void setWarningOutputDecorator(Function<String, String> warningOutputDecorator) {
-        this.warningOutputDecorator = warningOutputDecorator;
-    }
-
-    public void setErrorOutputDecorator(Function<String, String> errorOutputDecorator) {
-        this.errorOutputDecorator = errorOutputDecorator;
-    }
-
-    public void setCriticalOutputDecorator(Function<String, String> criticalOutputDecorator) {
-        this.criticalOutputDecorator = criticalOutputDecorator;
-    }
-
-    public String getInputName() {
-        return inputName;
-    }
-
-    public InputStream getInput() {
-        return input;
-    }
-
-    public PrintStream getOutput() {
-        return output;
-    }
-
-    public PrintStream getErrorOutput() {
-        return errorOutput;
-    }
-
-    public ErrorManager getErrorManager() {
-        return errorManager;
-    }
-
-    public String getPath() {
-        return path;
-    }
-
-    public void terminateSuccessfully() {
-        terminationFunction.run();
-    }
-
-    public void terminateExceptionally() {
-        errorTerminationFunction.run();
-    }
-
-    public String decoratePrompt(String prompt) {
-        return promptDecorator.apply(prompt);
-    }
-
-    public String decorateValueOutput(String valueOutput) {
-        return valueOutputDecorator.apply(valueOutput);
-    }
-
-    public String decorateWarningOutput(String warningOutput) {
-        return warningOutputDecorator.apply(warningOutput);
-    }
-
-    public String decorateErrorOutput(String errorOutput) {
-        return errorOutputDecorator.apply(errorOutput);
-    }
-
-    public String decorateCriticalOutput(String criticalOutput) {
-        return criticalOutputDecorator.apply(criticalOutput);
-    }
-}
diff --git a/src/main/kotlin/environment/RuntimeEnvironment.kt b/src/main/kotlin/environment/RuntimeEnvironment.kt
new file mode 100644
index 0000000..b2b3c75
--- /dev/null
+++ b/src/main/kotlin/environment/RuntimeEnvironment.kt
@@ -0,0 +1,56 @@
+package environment
+
+import error.ErrorManager
+
+import java.io.InputStream
+import java.io.PrintStream
+import java.util.function.Function
+
+object RuntimeEnvironment {
+
+    var inputName: String? = null
+    var input: InputStream? = null
+    var output: PrintStream? = null
+    var errorOutput: PrintStream? = null
+    var errorManager: ErrorManager? = null
+    var path: String? = null
+
+    // TODO - convert to function types ()-> Unit etc... once calling code is kotlin
+    var terminationFunction: Runnable? = null
+    var errorTerminationFunction: Runnable? = null
+    var promptDecorator: Function<String, String>? = null
+    var valueOutputDecorator: Function<String, String>? = null
+    var warningOutputDecorator: Function<String, String>? = null
+    var errorOutputDecorator: Function<String, String>? = null
+    var criticalOutputDecorator: Function<String, String>? = null
+
+    fun reset() {
+        inputName = null
+        input = null
+        output = null
+        errorOutput = null
+        errorManager = null
+        path = null
+        terminationFunction = null
+        errorTerminationFunction = null
+        promptDecorator = null
+        valueOutputDecorator = null
+        warningOutputDecorator = null
+        errorOutputDecorator = null
+        criticalOutputDecorator = null
+    }
+
+    fun terminateSuccessfully() {
+        terminationFunction!!.run()
+    }
+
+    fun terminateExceptionally() {
+        errorTerminationFunction!!.run()
+    }
+
+    fun decoratePrompt(prompt: String) = promptDecorator!!.apply(prompt)
+    fun decorateValueOutput(valueOutput: String) = valueOutputDecorator!!.apply(valueOutput)
+    fun decorateWarningOutput(warningOutput: String) = warningOutputDecorator!!.apply(warningOutput)
+    fun decorateErrorOutput(errorOutput: String) = errorOutputDecorator!!.apply(errorOutput)
+    fun decorateCriticalOutput(criticalOutput: String) = criticalOutputDecorator!!.apply(criticalOutput)
+}
diff --git a/src/main/kotlin/error/ErrorManager.kt b/src/main/kotlin/error/ErrorManager.kt
index ea4f1b1..595a086 100644
--- a/src/main/kotlin/error/ErrorManager.kt
+++ b/src/main/kotlin/error/ErrorManager.kt
@@ -11,13 +11,11 @@ import java.text.MessageFormat.format
  */
 class ErrorManager {
 
-    private val environment: RuntimeEnvironment = RuntimeEnvironment.getInstance()
-
     fun handle(lispException: LispException) {
         printMessage(lispException)
 
         if (isCritical(lispException))
-            environment.terminateExceptionally()
+            RuntimeEnvironment.terminateExceptionally()
     }
 
     private fun printMessage(lispException: LispException) {
@@ -26,7 +24,7 @@ class ErrorManager {
     }
 
     private fun selectOutputStream(severity: Severity): PrintStream {
-        return if (severity === WARNING) environment.output else environment.errorOutput
+        return if (severity === WARNING) RuntimeEnvironment.output!! else RuntimeEnvironment.errorOutput!!
     }
 
     private fun formatMessage(lispException: LispException): String {
@@ -34,7 +32,7 @@ class ErrorManager {
         val prefix = severity.toDisplayString()
         val message = format("[{0}] {1}", prefix, lispException.message)
 
-        return severity.decorate(message, environment)
+        return severity.decorate(message, RuntimeEnvironment)
     }
 
     private fun isCritical(lispException: LispException) = lispException.severity == CRITICAL
diff --git a/src/main/kotlin/error/Severity.kt b/src/main/kotlin/error/Severity.kt
index 3fd2cce..91e048d 100644
--- a/src/main/kotlin/error/Severity.kt
+++ b/src/main/kotlin/error/Severity.kt
@@ -6,21 +6,21 @@ enum class Severity {
 
     WARNING {
         override fun decorate(output: String, environment: RuntimeEnvironment): String =
-            environment.decorateWarningOutput(output)
+            RuntimeEnvironment.decorateWarningOutput(output)!!
 
         override fun toDisplayString() = "warning"
     },
 
     ERROR {
         override fun decorate(output: String, environment: RuntimeEnvironment): String =
-            environment.decorateErrorOutput(output)
+            RuntimeEnvironment.decorateErrorOutput(output)!!
 
         override fun toDisplayString() = "error"
     },
 
     CRITICAL {
         override fun decorate(output: String, environment: RuntimeEnvironment): String =
-            environment.decorateCriticalOutput(output)
+            RuntimeEnvironment.decorateCriticalOutput(output)!!
 
         override fun toDisplayString() = "critical"
     };
diff --git a/src/main/kotlin/function/builtin/EXIT.java b/src/main/kotlin/function/builtin/EXIT.java
index 5b91760..c8136a2 100644
--- a/src/main/kotlin/function/builtin/EXIT.java
+++ b/src/main/kotlin/function/builtin/EXIT.java
@@ -18,7 +18,7 @@ public class EXIT extends LispFunction {
     public EXIT(String name) {
         this.argumentValidator = new ArgumentValidator(name);
         this.argumentValidator.setMaximumNumberOfArguments(0);
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     @Override
diff --git a/src/main/kotlin/function/builtin/LOAD.java b/src/main/kotlin/function/builtin/LOAD.java
index d512990..2d080c0 100644
--- a/src/main/kotlin/function/builtin/LOAD.java
+++ b/src/main/kotlin/function/builtin/LOAD.java
@@ -32,7 +32,7 @@ public class LOAD extends LispFunction {
         this.argumentValidator = new ArgumentValidator(name);
         this.argumentValidator.setExactNumberOfArguments(1);
         this.argumentValidator.setEveryArgumentExpectedType(LispString.class);
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     @Override
diff --git a/src/main/kotlin/function/builtin/PRINT.java b/src/main/kotlin/function/builtin/PRINT.java
index c7a77d4..f8e69dc 100644
--- a/src/main/kotlin/function/builtin/PRINT.java
+++ b/src/main/kotlin/function/builtin/PRINT.java
@@ -16,7 +16,7 @@ public class PRINT extends LispFunction {
     public PRINT(String name) {
         this.argumentValidator = new ArgumentValidator(name);
         this.argumentValidator.setExactNumberOfArguments(1);
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     @Override
diff --git a/src/main/kotlin/function/builtin/special/Define.java b/src/main/kotlin/function/builtin/special/Define.java
index bfacfc4..e21ad93 100644
--- a/src/main/kotlin/function/builtin/special/Define.java
+++ b/src/main/kotlin/function/builtin/special/Define.java
@@ -31,7 +31,7 @@ public abstract class Define extends LispSpecialFunction {
         this.lambdaListValidator = new ArgumentValidator(functionName + "|parameter|");
         this.lambdaListValidator.setEveryArgumentExpectedType(Symbol.class);
 
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     @Override
diff --git a/src/main/kotlin/interpreter/LispInterpreter.java b/src/main/kotlin/interpreter/LispInterpreter.java
index c0f4cdf..a1eabb9 100644
--- a/src/main/kotlin/interpreter/LispInterpreter.java
+++ b/src/main/kotlin/interpreter/LispInterpreter.java
@@ -16,7 +16,7 @@ public class LispInterpreter {
     private LispParser parser;
 
     public LispInterpreter() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     public void interpretLanguageFiles(List<LanguageFile> languageFiles) {
diff --git a/src/main/kotlin/interpreter/LispInterpreterBuilderImpl.java b/src/main/kotlin/interpreter/LispInterpreterBuilderImpl.java
index 405ae83..f677bad 100644
--- a/src/main/kotlin/interpreter/LispInterpreterBuilderImpl.java
+++ b/src/main/kotlin/interpreter/LispInterpreterBuilderImpl.java
@@ -40,7 +40,7 @@ public class LispInterpreterBuilderImpl implements LispInterpreterBuilder {
     protected boolean isBuilt;
 
     protected LispInterpreterBuilderImpl() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
         this.inputName = "";
         this.isInteractive = true;
         this.isFileBased = false;
diff --git a/src/test/kotlin/acceptance/fixture/LispInterpreterFixture.java b/src/test/kotlin/acceptance/fixture/LispInterpreterFixture.java
index 307285d..0317354 100644
--- a/src/test/kotlin/acceptance/fixture/LispInterpreterFixture.java
+++ b/src/test/kotlin/acceptance/fixture/LispInterpreterFixture.java
@@ -20,7 +20,7 @@ public class LispInterpreterFixture {
 
     private static ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
     private static ExecutionContext executionContext = ExecutionContext.INSTANCE;
-    private static RuntimeEnvironment environment = RuntimeEnvironment.getInstance();
+    private static RuntimeEnvironment environment = RuntimeEnvironment.INSTANCE;
     private static LispInterpreter interpreter = null;
 
     public static void resetInterpreter() {
diff --git a/src/test/kotlin/application/MainTest.java b/src/test/kotlin/application/MainTest.java
index 49a9770..763c819 100644
--- a/src/test/kotlin/application/MainTest.java
+++ b/src/test/kotlin/application/MainTest.java
@@ -32,7 +32,7 @@ public class MainTest extends SymbolAndFunctionCleaner {
     private CountDownLatch latch;
 
     public MainTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void runInterpreterWithFile(String fileName) {
diff --git a/src/test/kotlin/environment/RuntimeEnvironmentTest.java b/src/test/kotlin/environment/RuntimeEnvironmentTest.java
deleted file mode 100644
index 22675af..0000000
--- a/src/test/kotlin/environment/RuntimeEnvironmentTest.java
+++ /dev/null
@@ -1,199 +0,0 @@
-package environment;
-
-import error.ErrorManager;
-import org.junit.After;
-import org.junit.Before;
-import org.junit.Test;
-
-import java.util.HashSet;
-import java.util.Set;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-
-public class RuntimeEnvironmentTest {
-
-    private static final String TERMINATED_SUCCESSFULLY = "TERMINATED_SUCCESSFULLY";
-    private static final String TERMINATED_EXCEPTIONALLY = "TERMINATED_EXCEPTIONALLY";
-
-    private RuntimeEnvironment environment;
-    private Set<String> indicatorSet;
-
-    public RuntimeEnvironmentTest() {
-        this.environment = RuntimeEnvironment.getInstance();
-    }
-
-    @Before
-    public void setUp() {
-        indicatorSet = new HashSet<>();
-        environment.reset();
-    }
-
-    @After
-    public void tearDown() {
-        environment.reset();
-    }
-
-    @Test
-    public void assignInputName() {
-        environment.setInputName("test");
-
-        assertEquals("test", environment.getInputName());
-    }
-
-    @Test
-    public void assignInput() {
-        environment.setInput(System.in);
-
-        assertEquals(System.in, environment.getInput());
-    }
-
-    @Test
-    public void assignOutput() {
-        environment.setOutput(System.out);
-
-        assertEquals(System.out, environment.getOutput());
-    }
-
-    @Test
-    public void assignErrorOutput() {
-        environment.setErrorOutput(System.err);
-
-        assertEquals(System.err, environment.getErrorOutput());
-    }
-
-    @Test
-    public void assignErrorManager() {
-        ErrorManager errorManager = new ErrorManager();
-        environment.setErrorManager(errorManager);
-
-        assertEquals(errorManager, environment.getErrorManager());
-    }
-
-    @Test
-    public void assignPath() {
-        environment.setPath("testpath/");
-
-        assertEquals("testpath/", environment.getPath());
-    }
-
-    @Test
-    public void assignTerminationFunction() {
-        environment.setTerminationFunction(() -> indicatorSet.add(TERMINATED_SUCCESSFULLY));
-        environment.terminateSuccessfully();
-
-        assertTrue(indicatorSet.contains(TERMINATED_SUCCESSFULLY));
-    }
-
-    @Test
-    public void assignErrorTerminationFunction() {
-        environment.setErrorTerminationFunction(() -> indicatorSet.add(TERMINATED_EXCEPTIONALLY));
-        environment.terminateExceptionally();
-
-        assertTrue(indicatorSet.contains(TERMINATED_EXCEPTIONALLY));
-    }
-
-    @Test
-    public void assignPromptDecorator() {
-        environment.setPromptDecorator(s -> "[" + s + "]");
-
-        assertEquals("[test]", environment.decoratePrompt("test"));
-    }
-
-    @Test
-    public void assignValueOutputDecorator() {
-        environment.setValueOutputDecorator(s -> "(" + s + ")");
-
-        assertEquals("(test)", environment.decorateValueOutput("test"));
-    }
-
-    @Test
-    public void assignWarningOutputDecorator() {
-        environment.setWarningOutputDecorator(s -> "|" + s + "|");
-
-        assertEquals("|test|", environment.decorateWarningOutput("test"));
-    }
-
-    @Test
-    public void assignErrorOutputDecorator() {
-        environment.setErrorOutputDecorator(s -> "{" + s + "}");
-
-        assertEquals("{test}", environment.decorateErrorOutput("test"));
-    }
-
-    @Test
-    public void assignCriticalOutputDecorator() {
-        environment.setCriticalOutputDecorator(s -> "/" + s + "/");
-
-        assertEquals("/test/", environment.decorateCriticalOutput("test"));
-    }
-
-    @Test
-    public void resetWorks() {
-        environment.setInputName("test");
-        environment.setInput(System.in);
-        environment.setOutput(System.out);
-        environment.setErrorOutput(System.err);
-        environment.setErrorManager(new ErrorManager());
-        environment.setPath("testpath/");
-        environment.setTerminationFunction(() -> indicatorSet.add(TERMINATED_SUCCESSFULLY));
-        environment.setErrorTerminationFunction(() -> indicatorSet.add(TERMINATED_EXCEPTIONALLY));
-        environment.setPromptDecorator(s -> "[" + s + "]");
-        environment.setValueOutputDecorator(s -> "(" + s + ")");
-        environment.setWarningOutputDecorator(s -> "|" + s + "|");
-        environment.setErrorOutputDecorator(s -> "{" + s + "}");
-        environment.setCriticalOutputDecorator(s -> "/" + s + "/");
-        environment.reset();
-
-        assertNull(environment.getInputName());
-        assertNull(environment.getInput());
-        assertNull(environment.getOutput());
-        assertNull(environment.getErrorOutput());
-        assertNull(environment.getErrorManager());
-        assertNull(environment.getPath());
-
-        try {
-            environment.terminateSuccessfully();
-            fail("terminateSuccessfully");
-        } catch (NullPointerException e) {
-        }
-
-        try {
-            environment.terminateExceptionally();
-            fail("terminateExceptionally");
-        } catch (NullPointerException e) {
-        }
-
-        try {
-            environment.decoratePrompt("");
-            fail("decoratePrompt");
-        } catch (NullPointerException e) {
-        }
-
-        try {
-            environment.decorateValueOutput("");
-            fail("decorateValueOutput");
-        } catch (NullPointerException e) {
-        }
-
-        try {
-            environment.decorateWarningOutput("");
-            fail("decorateWarningOutput");
-        } catch (NullPointerException e) {
-        }
-
-        try {
-            environment.decorateErrorOutput("");
-            fail("decorateErrorOutput");
-        } catch (NullPointerException e) {
-        }
-
-        try {
-            environment.decorateCriticalOutput("");
-            fail("decorateCriticalOutput");
-        } catch (NullPointerException e) {
-        }
-    }
-}
diff --git a/src/test/kotlin/environment/RuntimeEnvironmentTest.kt b/src/test/kotlin/environment/RuntimeEnvironmentTest.kt
new file mode 100644
index 0000000..776bbf3
--- /dev/null
+++ b/src/test/kotlin/environment/RuntimeEnvironmentTest.kt
@@ -0,0 +1,161 @@
+package environment
+
+import error.ErrorManager
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.TestInstance
+import org.junit.jupiter.api.TestInstance.Lifecycle.PER_CLASS
+import org.junit.jupiter.api.Assertions.assertThrows
+import java.util.HashSet
+import java.util.function.Function
+
+@TestInstance(PER_CLASS)
+class RuntimeEnvironmentTest {
+
+    companion object {
+        private const val TERMINATED_SUCCESSFULLY = "TERMINATED_SUCCESSFULLY"
+        private const val TERMINATED_EXCEPTIONALLY = "TERMINATED_EXCEPTIONALLY"
+    }
+
+    private var indicatorSet: MutableSet<String>? = null
+
+    @BeforeEach
+    fun setUp() {
+        indicatorSet = HashSet()
+        RuntimeEnvironment.reset()
+    }
+
+    @AfterEach
+    fun tearDown() {
+        RuntimeEnvironment.reset()
+    }
+
+    @Test
+    fun assignInputName() {
+        RuntimeEnvironment.inputName = "test"
+
+        assertThat(RuntimeEnvironment.inputName).isEqualTo("test")
+    }
+
+    @Test
+    fun assignInput() {
+        RuntimeEnvironment.input = System.`in`
+
+        assertThat(RuntimeEnvironment.input).isEqualTo(System.`in`)
+    }
+
+    @Test
+    fun assignOutput() {
+        RuntimeEnvironment.output = System.out
+
+        assertThat(RuntimeEnvironment.output).isEqualTo(System.out)
+    }
+
+    @Test
+    fun assignErrorOutput() {
+        RuntimeEnvironment.errorOutput = System.err
+
+        assertThat(RuntimeEnvironment.errorOutput).isEqualTo(System.err)
+    }
+
+    @Test
+    fun assignErrorManager() {
+        val errorManager = ErrorManager()
+        RuntimeEnvironment.errorManager = errorManager
+
+        assertThat(RuntimeEnvironment.errorManager).isEqualTo(errorManager)
+    }
+
+    @Test
+    fun assignPath() {
+        RuntimeEnvironment.path = "testpath/"
+
+        assertThat(RuntimeEnvironment.path).isEqualTo("testpath/")
+    }
+
+    @Test
+    fun assignTerminationFunction() {
+        RuntimeEnvironment.terminationFunction = Runnable { indicatorSet!!.add(TERMINATED_SUCCESSFULLY) }
+        RuntimeEnvironment.terminateSuccessfully()
+
+        assertThat(indicatorSet!!.contains(TERMINATED_SUCCESSFULLY)).isTrue()
+    }
+
+    @Test
+    fun assignErrorTerminationFunction() {
+        RuntimeEnvironment.errorTerminationFunction = Runnable { indicatorSet!!.add(TERMINATED_EXCEPTIONALLY) }
+        RuntimeEnvironment.terminateExceptionally()
+
+        assertThat(indicatorSet!!.contains(TERMINATED_EXCEPTIONALLY)).isTrue()
+    }
+
+    @Test
+    fun assignPromptDecorator() {
+        RuntimeEnvironment.promptDecorator = Function { s -> "[$s]" }
+
+        assertThat(RuntimeEnvironment.decoratePrompt("test")).isEqualTo("[test]")
+    }
+
+    @Test
+    fun assignValueOutputDecorator() {
+        RuntimeEnvironment.valueOutputDecorator = Function { s -> "($s)" }
+
+        assertThat(RuntimeEnvironment.decorateValueOutput("test")).isEqualTo("(test)")
+    }
+
+    @Test
+    fun assignWarningOutputDecorator() {
+        RuntimeEnvironment.warningOutputDecorator = Function { s -> "|$s|" }
+
+        assertThat(RuntimeEnvironment.decorateWarningOutput("test")).isEqualTo("|test|")
+    }
+
+    @Test
+    fun assignErrorOutputDecorator() {
+        RuntimeEnvironment.errorOutputDecorator = Function { s -> "{$s}" }
+
+        assertThat(RuntimeEnvironment.decorateErrorOutput("test")).isEqualTo("{test}")
+    }
+
+    @Test
+    fun assignCriticalOutputDecorator() {
+        RuntimeEnvironment.criticalOutputDecorator = Function { s -> "/$s/" }
+
+        assertThat(RuntimeEnvironment.decorateCriticalOutput("test")).isEqualTo("/test/")
+    }
+
+    @Test
+    fun resetWorks() {
+        RuntimeEnvironment.inputName = "test"
+        RuntimeEnvironment.input = System.`in`
+        RuntimeEnvironment.output = System.out
+        RuntimeEnvironment.errorOutput = System.err
+        RuntimeEnvironment.errorManager = ErrorManager()
+        RuntimeEnvironment.path = "testpath/"
+        RuntimeEnvironment.terminationFunction = Runnable { indicatorSet!!.add(TERMINATED_SUCCESSFULLY) }
+        RuntimeEnvironment.errorTerminationFunction = Runnable { indicatorSet!!.add(TERMINATED_EXCEPTIONALLY) }
+        RuntimeEnvironment.promptDecorator = Function { s -> "[$s]" }
+        RuntimeEnvironment.valueOutputDecorator = Function { s -> "($s)" }
+        RuntimeEnvironment.warningOutputDecorator = Function { s -> "|$s|" }
+        RuntimeEnvironment.errorOutputDecorator = Function { s -> "{$s}" }
+        RuntimeEnvironment.criticalOutputDecorator = Function { s -> "/$s/" }
+        RuntimeEnvironment.reset()
+
+        assertThat(RuntimeEnvironment.inputName).isNull()
+        assertThat(RuntimeEnvironment.input).isNull()
+        assertThat(RuntimeEnvironment.output).isNull()
+        assertThat(RuntimeEnvironment.errorOutput).isNull()
+        assertThat(RuntimeEnvironment.errorManager).isNull()
+        assertThat(RuntimeEnvironment.path).isNull()
+
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.terminateSuccessfully() }
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.terminateExceptionally() }
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.decoratePrompt("") }
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.decorateValueOutput("") }
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.decorateWarningOutput("") }
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.decorateErrorOutput("") }
+        assertThrows(NullPointerException::class.java) { RuntimeEnvironment.decorateCriticalOutput("") }
+    }
+}
diff --git a/src/test/kotlin/error/ErrorManagerTest.java b/src/test/kotlin/error/ErrorManagerTest.java
index fbc0fd3..2c30a6e 100644
--- a/src/test/kotlin/error/ErrorManagerTest.java
+++ b/src/test/kotlin/error/ErrorManagerTest.java
@@ -27,7 +27,7 @@ public class ErrorManagerTest {
     private RuntimeEnvironment environment;
 
     public ErrorManagerTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private ErrorManager createErrorManagerWithIndicators() {
diff --git a/src/test/kotlin/function/builtin/EXITTest.java b/src/test/kotlin/function/builtin/EXITTest.java
index c9a0965..fcf0217 100644
--- a/src/test/kotlin/function/builtin/EXITTest.java
+++ b/src/test/kotlin/function/builtin/EXITTest.java
@@ -19,7 +19,7 @@ public class EXITTest extends SymbolAndFunctionCleaner {
     private Set<String> indicatorSet;
 
     public EXITTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void assertTerminated() {
diff --git a/src/test/kotlin/function/builtin/LOADTest.java b/src/test/kotlin/function/builtin/LOADTest.java
index ae67a2b..5a54ec6 100644
--- a/src/test/kotlin/function/builtin/LOADTest.java
+++ b/src/test/kotlin/function/builtin/LOADTest.java
@@ -23,7 +23,7 @@ public class LOADTest extends SymbolAndFunctionCleaner {
     private RuntimeEnvironment environment;
 
     public LOADTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void assertWarningMessagePrinted() {
diff --git a/src/test/kotlin/function/builtin/PRINTTest.java b/src/test/kotlin/function/builtin/PRINTTest.java
index 4587939..32b2c3f 100644
--- a/src/test/kotlin/function/builtin/PRINTTest.java
+++ b/src/test/kotlin/function/builtin/PRINTTest.java
@@ -19,7 +19,7 @@ public class PRINTTest extends SymbolAndFunctionCleaner {
     private ByteArrayOutputStream outputStream;
 
     public PRINTTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void assertPrinted(String expected) {
diff --git a/src/test/kotlin/function/builtin/special/DEFINE_SPECIALTest.java b/src/test/kotlin/function/builtin/special/DEFINE_SPECIALTest.java
index 1453e5f..62a2015 100644
--- a/src/test/kotlin/function/builtin/special/DEFINE_SPECIALTest.java
+++ b/src/test/kotlin/function/builtin/special/DEFINE_SPECIALTest.java
@@ -24,7 +24,7 @@ public class DEFINE_SPECIALTest extends SymbolAndFunctionCleaner {
     private RuntimeEnvironment environment;
 
     public DEFINE_SPECIALTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void assertSomethingPrinted() {
diff --git a/src/test/kotlin/function/builtin/special/DEFMACROTest.java b/src/test/kotlin/function/builtin/special/DEFMACROTest.java
index 2936242..15e81de 100644
--- a/src/test/kotlin/function/builtin/special/DEFMACROTest.java
+++ b/src/test/kotlin/function/builtin/special/DEFMACROTest.java
@@ -24,7 +24,7 @@ public class DEFMACROTest extends SymbolAndFunctionCleaner {
     private RuntimeEnvironment environment;
 
     public DEFMACROTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void assertSomethingPrinted() {
diff --git a/src/test/kotlin/function/builtin/special/DEFUNTest.java b/src/test/kotlin/function/builtin/special/DEFUNTest.java
index ed19758..d9f11eb 100644
--- a/src/test/kotlin/function/builtin/special/DEFUNTest.java
+++ b/src/test/kotlin/function/builtin/special/DEFUNTest.java
@@ -24,7 +24,7 @@ public class DEFUNTest extends SymbolAndFunctionCleaner {
     private RuntimeEnvironment environment;
 
     public DEFUNTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
     }
 
     private void assertSomethingPrinted() {
diff --git a/src/test/kotlin/interpreter/LispInterpreterTest.java b/src/test/kotlin/interpreter/LispInterpreterTest.java
index 659f096..53f1310 100644
--- a/src/test/kotlin/interpreter/LispInterpreterTest.java
+++ b/src/test/kotlin/interpreter/LispInterpreterTest.java
@@ -32,7 +32,7 @@ public class LispInterpreterTest {
     private LispInterpreterBuilder builder;
 
     public LispInterpreterTest() {
-        this.environment = RuntimeEnvironment.getInstance();
+        this.environment = RuntimeEnvironment.INSTANCE;
 
         this.builder = new LispInterpreterBuilderImpl() {