diff --git a/mfdez1982/StringCalculator.groovy b/mfdez1982/StringCalculator.groovy
new file mode 100644
index 0000000..6b10edd
--- /dev/null
+++ b/mfdez1982/StringCalculator.groovy
@@ -0,0 +1,47 @@
+class StringCalculator
+{
+	def input
+	def separatorSet = '\n,'
+	def SEP_HEADER_PATTERN = '//(.+)\n'
+	
+	Integer add(String stringNumbers)
+	{
+		input = stringNumbers
+		parseAndRemoveSeparatorHeader()
+		if (input.contains('-'))
+			parseNegativeNumbersAndThrowException();
+		else
+		{
+			replaceSeparatorsWithSpaces()
+			return add()
+		}
+	}
+	
+	private Integer add()
+	{	
+		Integer total = 0;
+		for (String number : input.split())
+			total += number.toInteger()<1000 ? number.toInteger() : 0
+		return total
+	}
+	
+	private void parseAndRemoveSeparatorHeader()
+	{
+		separatorSet += input.find(SEP_HEADER_PATTERN){ match, sep -> return sep};
+		input = input - ~SEP_HEADER_PATTERN
+	}	
+	
+	private void replaceSeparatorsWithSpaces()
+	{
+		input = input.tr(separatorSet, ' ')
+	}
+	
+	private void parseNegativeNumbersAndThrowException()
+	{
+		def exceptionMessage = 'negatives not allowed: '
+		def matcher = input =~ /(-\d*)/
+		for(String[] match : matcher)
+			exceptionMessage += ' ' + match[0]
+		throw new Exception(exceptionMessage)
+	}
+}
\ No newline at end of file
diff --git a/mfdez1982/StringCalculatorTest.groovy b/mfdez1982/StringCalculatorTest.groovy
new file mode 100644
index 0000000..9beb8d3
--- /dev/null
+++ b/mfdez1982/StringCalculatorTest.groovy
@@ -0,0 +1 @@
+import groovy.util.GroovyTestCase

class StringCalculatorTest extends GroovyTestCase
{
	def calculator = new StringCalculator()
	
	void testEmptyString()
	{
		assertEquals 0, calculator.add("")
	}

	void testZero()
	{
		assertEquals 0, calculator.add("0")
	}
	
	void testOne()
	{
		assertEquals 1, calculator.add("1")
	}
	
	void testZeroPlusOne()
	{
		assertEquals 1, calculator.add("0,1")
	}
	
	void testOnePlusTwo()
	{
		assertEquals 3, calculator.add("1,2")
	}
	
	void testWithThreeNumbers()
	{
		assertEquals 6, calculator.add("1,2,3")
	}
	
	void testWithUndeterminedNumberOfNumbers()
	{
		assertEquals 15, calculator.add("0,1,2,3,4,5")
	}
	
	void testNewLineSeparator()
	{
		assertEquals 3, calculator.add("1\n2")
	}
	
	void testComaAndNewLineSeparatorMixed()
	{
		assertEquals 15, calculator.add("1\n2,3,4\n5")
	}

	void testCustomSeparator()
	{
		assertEquals 3, calculator.add("//;\n1;2")
	}

	void testOnlyNegativeNumberNotAllowed()
	{
		def msg = shouldFail {calculator.add("-1")}
		println msg
	}	
	
	void testNegativeNumberNotAllowed()
	{
		def msg = shouldFail {calculator.add("8,-6,9")}
		println msg
	}	
	
	void testSeveralNegativeNumberNotAllowed()
	{
		def msg = shouldFail {calculator.add("8,-6,9,-3")}
		println msg
	}	
	
	void testNumbersBiggerThanThousandShouldBeIgnored()
	{
		assertEquals 4, calculator.add("1,2000,3")
	}
	
	void testCustomSeparatorOfVariableLength()
	{
		assertEquals 4, calculator.add("//[***]\n1***2000***3")
	}
	
	void testMultipleSeparators()
	{
		assertEquals 10, calculator.add("//[*][%][+]\n1*2%3+4")
	}
	
	void testMultipleSeparatorsWithVariableLength()
	{
		assertEquals 10, calculator.add("//[***][%][+]\n1***2%3+4")
	}
	
	void testMultipleSeparatorsWithVariableLengthAndNumbersBiggerThanThousand()
	{
		assertEquals 8, calculator.add("//[***][%%][++++]\n1***2000%%3++++4")
	}
}
\ No newline at end of file