The following test case in the MainSpec module 
is used to test the decoding and encoding functions defined in the Main module , specifically decodePerson and encodePerson. commit
This ensures that the decoding and encoding functions work correctly by comparing the actual output with the expected output.
Here's an explanation of the test case:
module MainSpec exposing (suite) import Expect import Json.Decode as Decode import Json.Encode as Encode import Main exposing (Person, decodePerson, encodePerson) import Test exposing (Test, test)
rawData: It represents a JSON string that simulates the input data for decoding. The JSON object contains "name", "age", and "hobbies" fields.
rawData : String rawData = """ { "name": "John Doe", "age": 25, "hobbies": ["reading", "running", "cooking"] } """
suite: It defines a test suite using Test.describe to group related tests together.
suite : Test suite = Test.describe "Main" [ test "decodePerson" <| […] , test "encodePerson" <| […] ]
The suite has two individual tests.
test "decodePerson": It tests the decodePerson function by decoding the rawData JSON string.
-- JSON Decoding (in Main.elm) decodePerson : Decoder Person decodePerson = Decode.succeed Person |> required "name" Decode.string |> required "age" Decode.int |> required "hobbies" (Decode.list Decode.string)
Inside the decodePerson test,
\() -> let jsonData = rawData expectedPerson = Person "John Doe" 25 [ "reading", "running", "cooking" ] decoded = Decode.decodeString decodePerson jsonData in Expect.equal decoded (Ok expectedPerson)
the JSON string is decoded using Decode.decodeString decodePerson. The expected result, expectedPerson, is a predefined Person record with values corresponding to the fields in rawData. Finally, Expect.equal is used to compare the decoded result with the expected result.
test "encodePerson":
It tests the encodePerson function by encoding a Person record.
Inside the test case, a person record is created with specific values.
The expected JSON string, expectedJson, is a manually constructed string that matches the structure of the encoded person record.
The encodePerson function is called with the person record, and the resulting JSON string is stored in encoded.
Finally, Expect.equal is used to compare the encoded result with the expected JSON string. github