Add PhoneNumber example and test

PhoneNumber/PhoneNumberExample.elm

@@ -0,0 +1,24 @@
+module PhoneNumberExample where
+
+import String
+
+nums = ['1','2','3','4','5','6','7','8','9','0']
+
+getNumber : String -> String
+getNumber text = getValidNum (String.filter isDigit text)
+
+isDigit : Char -> Bool
+isDigit char = List.any (\n -> n == char) nums
+
+getValidNum : String -> String
+getValidNum num =
+  if String.length num == 10 then num else
+    if (String.length num == 11) && (String.left 1 num == "1") then String.dropLeft 1 num else
+      String.repeat 10 "0"
+
+printPretty : String -> String
+printPretty input = formatNumber (getNumber input)
+
+
+formatNumber : String -> String
+formatNumber input = String.concat ["(", (String.slice 0 3 input),  ") ", (String.slice 3 6 input), "-", (String.slice 6 10 input)]

PhoneNumber/PhoneNumberTest.elm

@@ -0,0 +1,28 @@
+module PhoneNumberTest where
+
+-- TODO - remove example inclusion once Problem sets are ready to go live or CI is set up.
+
+import PhoneNumberExample exposing (getNumber, printPretty)
+
+import ElmTest.Test exposing (test, Test, suite)
+import ElmTest.Assertion exposing (assert, assertEqual)
+import ElmTest.Runner.Element exposing (runDisplay)
+
+tests : Test
+tests = suite "PhoneNumber test suite"
+      [
+        test "cleans number" (assertEqual "1234567890" (getNumber "(123) 456-7890")),
+        test "cleans number with dots" (assertEqual "1234567890" (getNumber "123.456.7890")),
+        test "valid when 11 digits and first is 1" (assertEqual "1234567890" (getNumber "11234567890")),
+        test "invalid when 11 digits" (assertEqual "0000000000" (getNumber "21234567890")),
+        test "invalid when 9 digits" (assertEqual "0000000000" (getNumber "123456789")),
+        test "invalid when 12 digits" (assertEqual "0000000000" (getNumber "123456789012")),
+        test "invalid when empty" (assertEqual "0000000000" (getNumber "")),
+        test "invalid when no digits present" (assertEqual "0000000000" (getNumber " (-) ")),
+        test "valid with leading characters" (assertEqual "1234567890" (getNumber "my number is 123 456 7890")),
+        test "valid with trailing characters" (assertEqual "1234567890" (getNumber "123 456 7890 - bob")),
+        test "pretty print" (assertEqual "(123) 456-7890" (printPretty "1234567890")),
+        test "pretty print with full us phone number" (assertEqual "(123) 456-7890" (printPretty "11234567890"))
+      ]
+
+main = runDisplay tests

elm-package.json

@@ -26,7 +26,8 @@
         "Strain",
         "SpaceAge",
         "Anagram",
-        "NucleotideCount"
+        "NucleotideCount",
+        "PhoneNumber"
     ],
     "exposed-modules": [],
     "dependencies": {