diff --git a/src/test/java/com/mattrixwv/CipherStreamJava/monoSubstitution/TestSubstitution.java b/src/test/java/com/mattrixwv/CipherStreamJava/monoSubstitution/TestSubstitution.java
new file mode 100644
index 0000000..04000de
--- /dev/null
+++ b/src/test/java/com/mattrixwv/CipherStreamJava/monoSubstitution/TestSubstitution.java
@@ -0,0 +1,467 @@
+//CipherStreamJava/src/test/java/com/mattrixwv/CipherStreamJava/monoSubstitution/TestSubstitution.java
+//Mattrixwv
+// Created: 02-22-22
+//Modified: 02-22-22
+package com.mattrixwv.CipherStreamJava.monoSubstitution;
+
+
+import static org.junit.Assert.assertEquals;
+
+import com.mattrixwv.CipherStreamJava.exceptions.InvalidInputException;
+import com.mattrixwv.CipherStreamJava.exceptions.InvalidKeywordException;
+
+import org.junit.Test;
+
+
+public class TestSubstitution{
+	@Test
+	public void testEncode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(true, true, true);
+
+		//Test lowercase encoding
+		String inputString = "messagetoencode";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "oguucigvqgpeqfg";
+		String output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed lowercase encoding.", correctOutput, output);
+		//Test uppercase encoding
+		inputString = "MESSAGETOENCODE";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed uppercase encoding.", correctOutput, output);
+
+		//Test whitespace encoding
+		inputString = "message to encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "oguucig vq gpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed whitespace encoding.", correctOutput, output);
+
+		//Test symbol encoding
+		inputString = "message*to+encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "oguucig*vq+gpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed symbol encoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol encoding
+		inputString = "Message to^encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "Oguucig vq^gpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed mixed case, whitespace, symbol encoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number encoding with long key
+		inputString = "Message to&encode 123";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "Oguucig vq&gpeqfg 876";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed mixed case, whitespace, symbol, number encoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoCapitalEncode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(false, true, true);
+
+		//Test lowercase encoding
+		String inputString = "messagetoencode";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "OGUUCIGVQGPEQFG";
+		String output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital lowercase encoding.", correctOutput, output);
+		//Test uppercase encoding
+		inputString = "MESSAGETOENCODE";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital uppercase encoding.", correctOutput, output);
+
+		//Test whitespace encoding
+		inputString = "message to encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIG VQ GPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital whitespace encoding.", correctOutput, output);
+
+		//Test symbol encoding
+		inputString = "message*to+encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIG*VQ+GPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital symbol encoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol encoding
+		inputString = "Message to^encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIG VQ^GPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital mixed case, whitespace, symbol encoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number encoding with long key
+		inputString = "Message to&encode 123";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "OGUUCIG VQ&GPEQFG 876";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital mixed case, whitespace, symbol, number encoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoWhitespaceEncode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(true, false, true);
+
+		//Test lowercase encoding
+		String inputString = "messagetoencode";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "oguucigvqgpeqfg";
+		String output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no whitespace lowercase encoding.", correctOutput, output);
+		//Test uppercase encoding
+		inputString = "MESSAGETOENCODE";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no whitespace uppercase encoding.", correctOutput, output);
+
+		//Test whitespace encoding
+		inputString = "message to encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "oguucigvqgpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no whitespace whitespace encoding.", correctOutput, output);
+
+		//Test symbol encoding
+		inputString = "message*to+encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "oguucig*vq+gpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no whitespace symbol encoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol encoding
+		inputString = "Message to^encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "Oguucigvq^gpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no whitespace mixed case, whitespace, symbol encoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number encoding with long key
+		inputString = "Message to&encode 123";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "Oguucigvq&gpeqfg876";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no whitespace mixed case, whitespace, symbol, number encoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoSymbolEncode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(true, true, false);
+
+		//Test lowercase encoding
+		String inputString = "messagetoencode";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "oguucigvqgpeqfg";
+		String output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no symbol lowercase encoding.", correctOutput, output);
+		//Test uppercase encoding
+		inputString = "MESSAGETOENCODE";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no symbol uppercase encoding.", correctOutput, output);
+
+		//Test whitespace encoding
+		inputString = "message to encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "oguucig vq gpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no symbol whitespace encoding.", correctOutput, output);
+
+		//Test symbol encoding
+		inputString = "message*to+encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "oguucigvqgpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no symbol symbol encoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol encoding
+		inputString = "Message to^encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "Oguucig vqgpeqfg";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no symbol mixed case, whitespace, symbol encoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number encoding with long key
+		inputString = "Message to&encode 123";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "Oguucig vqgpeqfg ";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no symbol mixed case, whitespace, symbol, number encoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoCapitalWhitespaceSymbolEncode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(false, false, false);
+
+		//Test lowercase encoding
+		String inputString = "messagetoencode";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "OGUUCIGVQGPEQFG";
+		String output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital lowercase encoding.", correctOutput, output);
+		//Test uppercase encoding
+		inputString = "MESSAGETOENCODE";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital uppercase encoding.", correctOutput, output);
+
+		//Test whitespace encoding
+		inputString = "message to encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital whitespace encoding.", correctOutput, output);
+
+		//Test symbol encoding
+		inputString = "message*to+encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital symbol encoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol encoding
+		inputString = "Message to^encode";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital mixed case, whitespace, symbol encoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number encoding with long key
+		inputString = "Message to&encode 123";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "OGUUCIGVQGPEQFG";
+		output = cipher.encode(key, inputString);
+		assertEquals("Substitution failed no capital mixed case, whitespace, symbol, number encoding with long key.", correctOutput, output);
+	}
+
+
+	@Test
+	public void testDecode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(true, true, true);
+
+		//Test lowercase decoding
+		String inputString = "oguucigvqgpeqfg";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "messagetoencode";
+		String output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed lowercase decoding.", correctOutput, output);
+		//Test uppercase decoding
+		inputString = "OGUUCIGVQGPEQFG";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed uppercase decoding.", correctOutput, output);
+
+		//Test whitespace decoding
+		inputString = "oguucig vq gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "message to encode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed whitespace decoding.", correctOutput, output);
+
+		//Test symbol decoding
+		inputString = "oguucig*vq+gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "message*to+encode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed whitespace decoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol decoding
+		inputString = "Oguucig vq^gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "Message to^encode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed mixed case, whitespace, symbol decoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number decoding with long key
+		inputString = "Oguucig vq&gpeqfg 876";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "Message to&encode 123";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed mixed case, whitespace, symbol, number decoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoCapitalDecode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(false, true, true);
+
+		//Test lowercase decoding
+		String inputString = "oguucigvqgpeqfg";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "MESSAGETOENCODE";
+		String output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no capital lowercase decoding.", correctOutput, output);
+		//Test uppercase decoding
+		inputString = "OGUUCIGVQGPEQFG";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no capital uppercase decoding.", correctOutput, output);
+
+		//Test whitespace decoding
+		inputString = "oguucig vq gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGE TO ENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no capital whitespace decoding.", correctOutput, output);
+
+		//Test symbol decoding
+		inputString = "oguucig*vq+gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGE*TO+ENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no capital whitespace decoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol decoding
+		inputString = "Oguucig vq^gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGE TO^ENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no capital mixed case, whitespace, symbol decoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number decoding with long key
+		inputString = "Oguucig vq&gpeqfg 876";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "MESSAGE TO&ENCODE 123";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no capital mixed case, whitespace, symbol, number decoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoWhitespaceDecode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(true, false, true);
+
+		//Test lowercase decoding
+		String inputString = "oguucigvqgpeqfg";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "messagetoencode";
+		String output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no whitespace lowercase decoding.", correctOutput, output);
+		//Test uppercase decoding
+		inputString = "OGUUCIGVQGPEQFG";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no whitespace uppercase decoding.", correctOutput, output);
+
+		//Test whitespace decoding
+		inputString = "oguucig vq gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "messagetoencode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no whitespace whitespace decoding.", correctOutput, output);
+
+		//Test symbol decoding
+		inputString = "oguucig*vq+gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "message*to+encode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no whitespace whitespace decoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol decoding
+		inputString = "Oguucig vq^gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "Messageto^encode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no whitespace mixed case, whitespace, symbol decoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number decoding with long key
+		inputString = "Oguucig vq&gpeqfg 876";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "Messageto&encode123";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no whitespace mixed case, whitespace, symbol, number decoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoSymbolDecode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(true, true, false);
+
+		//Test lowercase decoding
+		String inputString = "oguucigvqgpeqfg";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "messagetoencode";
+		String output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no symbol lowercase decoding.", correctOutput, output);
+		//Test uppercase decoding
+		inputString = "OGUUCIGVQGPEQFG";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no symbol uppercase decoding.", correctOutput, output);
+
+		//Test whitespace decoding
+		inputString = "oguucig vq gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "message to encode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no symbol whitespace decoding.", correctOutput, output);
+
+		//Test symbol decoding
+		inputString = "oguucig*vq+gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "messagetoencode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no symbol whitespace decoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol decoding
+		inputString = "Oguucig vq^gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "Message toencode";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed mixed no symbol case, whitespace, symbol decoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number decoding with long key
+		inputString = "Oguucig vq&gpeqfg 876";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "Message toencode ";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed no symbol mixed case, whitespace, symbol, number decoding with long key.", correctOutput, output);
+	}
+
+	@Test
+	public void testNoCapitalWhitespaceSymbolDecode() throws InvalidKeywordException, InvalidInputException{
+		Substitution cipher = new Substitution(false, false, false);
+
+		//Test lowercase decoding
+		String inputString = "oguucigvqgpeqfg";
+		String key = "cdefghijklmnopqrstuvwxyzab";
+		String correctOutput = "MESSAGETOENCODE";
+		String output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed secure lowercase decoding.", correctOutput, output);
+		//Test uppercase decoding
+		inputString = "OGUUCIGVQGPEQFG";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed secure uppercase decoding.", correctOutput, output);
+
+		//Test whitespace decoding
+		inputString = "oguucig vq gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed secure whitespace decoding.", correctOutput, output);
+
+		//Test symbol decoding
+		inputString = "oguucig*vq+gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed secure whitespace decoding.", correctOutput, output);
+
+		//Test mixed case, whitespace, symbol decoding
+		inputString = "Oguucig vq^gpeqfg";
+		key = "cdefghijklmnopqrstuvwxyzab";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed secure mixed case, whitespace, symbol decoding.", correctOutput, output);
+		//Test mixed case, whitespace, symbol, number decoding with long key
+		inputString = "Oguucig vq&gpeqfg 876";
+		key = "cdefghijklmnopqrstuvwxyzab9876543210";
+		correctOutput = "MESSAGETOENCODE";
+		output = cipher.decode(key, inputString);
+		assertEquals("Substitution failed secure mixed case, whitespace, symbol, number decoding with long key.", correctOutput, output);
+	}
+}