diff --git a/bin/Spreadsheet.class b/bin/Spreadsheet.class
index 92b411f..cbecc39 100644
Binary files a/bin/Spreadsheet.class and b/bin/Spreadsheet.class differ
diff --git a/bin/SpreadsheetTest.class b/bin/SpreadsheetTest.class
index e7086bd..dcc0df0 100644
Binary files a/bin/SpreadsheetTest.class and b/bin/SpreadsheetTest.class differ
diff --git a/src/Spreadsheet.java b/src/Spreadsheet.java
index e4f120b..5eed6e9 100644
--- a/src/Spreadsheet.java
+++ b/src/Spreadsheet.java
@@ -1,18 +1,130 @@
+import java.util.HashMap;
 
 public class Spreadsheet {
 
+	HashMap<String, String> spreadsheet;
+	
+	public Spreadsheet() {
+		this.spreadsheet = new HashMap<String, String>();
+	}
 	public String get(String cell) {
-		// to be implemented
-		return null;
+		
+		return spreadsheet.get(cell);
 	}
 	
 	public void set(String cell, String value) {
-		// to be implemented
+		spreadsheet.put(cell, value);
 	}
 	
 	public String evaluate(String cell) {
-		// to be implemented
-		return null;
+		String value = "";
+		if(get(cell).charAt(0) == '-') {
+			value = get(cell);
+		}
+		else if(get(cell).charAt(0) == '=') {
+			value = checkEqual(get(cell));
+		}
+		else if(Character.isDigit(get(cell).charAt(0))) {
+			value = checkDigit(get(cell));
+		}
+		else if(get(cell).charAt(0) == '\'') {
+			value = checkString(get(cell));
+		} else {
+			value = "#Error";
+		}
+		return value;
+	}
+	
+	private String checkEqual(String string) {
+		if(string.charAt(1) == '\'') {
+			return checkForStringOperations(string);
+		} else if(Character.isLetter(string.charAt(1))) {
+			String otherValue = get(string.replaceAll("=", ""));
+			if(otherValue.charAt(0) == '\'') {
+				return checkString(otherValue);
+			} else if(Character.isDigit(otherValue.charAt(0))) {
+				return checkDigit(otherValue);
+			} else if (otherValue.charAt(0) == '-') {
+				return otherValue;
+			} else if(otherValue.charAt(0) == '=') {
+				return checkForCirculation(string, otherValue);
+			}
+		} else if(Character.isDigit(string.charAt(1))) {	
+			return checkForOperations(string);
+		}
+		
+		return "#Error";
+	}
+	private String checkForStringOperations(String string) {
+		if((string.contains("&")) && (string.charAt(1) == '\'') && (string.charAt(string.length()-1) == '\'')) {
+			for(int i = 0; i < string.length(); i++) {
+				if(string.charAt(i) == '&' && string.charAt(i-1) == '\'' && string.charAt(i+1) == '\'') {
+					return string.replaceAll("['=&]", "");
+				}
+				
+			}
+			
+		} else if ( string.charAt(string.length()-1) == '\'') {
+			return checkString(string.replaceAll("=", ""));
+		}
+			
+		 return "#Error";
+	}
+	private String checkForOperations(String string) {
+		String s = string;
+		int sum = 0;
+		for(int i = 1; i < s.length(); i++) {
+			if(Character.isLetter(s.charAt(i))) {
+				return "#Error";
+			}
+			switch(string.charAt(i)) {
+				case '+':
+					sum += Character.getNumericValue(s.charAt(i-1)) + Character.getNumericValue(s.charAt(i+1));
+					break;
+				case '-':
+					sum += Character.getNumericValue(s.charAt(i-1)) - Character.getNumericValue(s.charAt(i+1));
+					break;
+				case '*':
+					sum += Character.getNumericValue(s.charAt(i-1)) * Character.getNumericValue(s.charAt(i+1));
+					break;
+				case '/':
+					sum += Character.getNumericValue(s.charAt(i-1)) / Character.getNumericValue(s.charAt(i+1));
+					break;
+				case '%':
+					sum += Character.getNumericValue(s.charAt(i-1)) % Character.getNumericValue(s.charAt(i+1));
+					break;
+			}
+		}
+		return Integer.toString(sum);
+	}
+	private String checkForCirculation(String string, String otherValue) {
+		String key = "=";
+		for(Object o : spreadsheet.keySet()) {
+			if(spreadsheet.get(o).equals(string)) {
+				key += o;
+			}
+			if(key.equals(otherValue)) {
+				return "#Circular";
+			}
+		}
+		return otherValue;
+	}
+	
+	private String checkString(String string) {
+		if(string.charAt(string.length()-1) == '\'') {
+			return string.replaceAll("'", "");
+		} else {
+			return "#Error";
+		}
+	}
+	
+	private String checkDigit(String string) {
+		for(int i = 0 ; i < string.length(); i++) {
+			if(!Character.isDigit(string.charAt(i))) {
+				return "#Error";
+			}
+		}
+		return string;
 	}
 	
 }
diff --git a/tests/SpreadsheetTest.java b/tests/SpreadsheetTest.java
index 9e0936a..f17e993 100644
--- a/tests/SpreadsheetTest.java
+++ b/tests/SpreadsheetTest.java
@@ -6,10 +6,100 @@
 
 public class SpreadsheetTest {
 
-	@Test
-	public void test() {
-		fail("Not yet implemented");
-		
+	Spreadsheet spreadsheet = new Spreadsheet();
+	
+	@Test public void testSetandGet_1_1() {
+		spreadsheet.set("A1", "1");
+		String value = spreadsheet.get("A1");
+		assertEquals(value,"1");
 	}
 
+	@Test public void testNegativeIntegers_minus1_minus1() {
+		spreadsheet.set("A1", "-1");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"-1");
+	}
+	
+	@Test public void testWronglyFormattedIntegers_5A_Error() {
+		spreadsheet.set("A1", "5A");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"#Error");
+	}
+	
+	@Test public void testStringHandling_astring_astring() {
+		spreadsheet.set("A1", "'a string'");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"a string");
+	}
+	
+	@Test public void testUnquotedStrings_astring_error() {
+		spreadsheet.set("A1", "'a string");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"#Error");
+	}
+	
+	@Test public void testUnquotedStrings2_astring_error() {
+		spreadsheet.set("A1", "a string'");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"#Error");
+	}
+	
+	@Test public void testEvaluateSimpleFormulas_isEqualaString_aString() {
+		spreadsheet.set("A1", "='a string'");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"a string");
+	}
+	
+	@Test public void testEvaluate_SimpleFormulasWithErrors_equalaString_error() {
+		spreadsheet.set("A1", "='a string");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"#Error");
+	}
+	
+	@Test public void testCellReferences_5_5() {
+		spreadsheet.set("A1", "5");
+		spreadsheet.set("A2", "=A1");
+		String value = spreadsheet.evaluate("A2");
+		assertEquals(value,"5");
+	}
+	
+	@Test public void testWrongCellReferences_5A_error() {
+		spreadsheet.set("A1", "5A");
+		spreadsheet.set("A2", "=A1");
+		String value = spreadsheet.evaluate("A2");
+		assertEquals(value,"#Error");
+	}
+
+	@Test public void testDetectCircularReferences_A1_circular() {
+		spreadsheet.set("A1", "=A2");
+		spreadsheet.set("A2", "=A1");
+		String value = spreadsheet.evaluate("A2");
+		assertEquals(value,"#Circular");
+	}
+
+	@Test public void testIntegerOperations_1plus1multi2_4() {
+		spreadsheet.set("A1", "=1+1*2");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"4");
+	}
+	
+	@Test public void testErrorsInIntegerOperations_A1_error() {
+		spreadsheet.set("A1", "=1+1A");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"#Error");
+	}
+	
+	@Test public void testStringOperations_A1_astring() {
+		spreadsheet.set("A1", "='a'&'string'");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"astring");
+	}
+	
+	@Test public void testErrorsInStringOperations_A1_error() {
+		spreadsheet.set("A1", "='a&'string'");
+		String value = spreadsheet.evaluate("A1");
+		assertEquals(value,"#Error");
+	}
+	
+	
 }