adding test harness

exercises/exercise2/testPresidents.js

+// Make a smaller array of the test data to run on
+// and export it
+// e.g. 3 presidents born in the 1800's , 2 in the pre 1800's  and 1 post 1800's
+

exercises/exercise2/tests.js

+// import data from testData.js and assign it to a variable
+
+function testFilter(testData, expectedData) {
+    let result = testData.filter()
+    if (result === expectedData) {
+        console.log('filter passed')
+    }  else {
+        // can also throw an error
+        console.log('filter failed')
+    }
+}
+
+testFilter()
\ No newline at end of file