voicera/tester

// Package ddt provides utilities to populate test cases for data-driven tests.
package ddt

import (
    "encoding/json"
    "errors"
    "io/ioutil"
    "runtime"
    "strings"
)

const (
    cannotGetTestFunctionNameErrorMessage = "ddt: cannot determine test function name required to load JSON file"
)

type dataDrivenTest struct {
    TestCases json.RawMessage `json:"testCases,omitempty"`
}

// LoadTestCasesFromDerivedJSONFile loads test cases from a JSON file whose path
// is derived from the caller's test function name and file. The file path is
// "<package under test>/_ddt/<basename of test file>.json"; for example,
// "hitchhiker/_ddt/question_test.json" with the following schema:
//
//  {"testCases": [{<properties of the test case to unmarshal>}, ...]}
//
// For example, the JSON content may look like the following:
//
//  {
//    "testCases": [
//      {
//        "id": "The Ultimate Question",
//        "input": {
//          "question": "What do you get when you multiply six by nine?",
//          "timeoutInHours": 65700000000,
//          "config": {"base": 13}
//        },
//        "expected": {
//          "answer": "42",
//          "error": null
//        }
//      }
//    ]
//  }
//
// The details of the test case struct are left for the tester to specify.
func LoadTestCasesFromDerivedJSONFile(testCasesToLoad interface{}) error {
    testFunctionName, err := getTestFunctionName()
    if err != nil {
        return err
    }
    testDataFilePath := "_ddt/" + testFunctionName + ".json"

    fileContent, err := ioutil.ReadFile(testDataFilePath)
    if err != nil {
        return err
    }

    test := &dataDrivenTest{}
    err = json.Unmarshal(fileContent, &test)
    if err != nil {
        return err
    }

    if len(test.TestCases) == 0 {
        return errors.New("ddt: cannot load test cases from " + testFunctionName + ".json")
    }
    return json.Unmarshal(test.TestCases, &testCasesToLoad)
}

func getTestFunctionName() (string, error) {
    for stackFramesToSkip := 2; ; stackFramesToSkip++ {
        callerProgramCounter, _, _, ok := runtime.Caller(stackFramesToSkip)
        if !ok {
            return "", errors.New(cannotGetTestFunctionNameErrorMessage)
        }
        functionFullPath := runtime.FuncForPC(callerProgramCounter).Name()
        functionName := functionFullPath[strings.LastIndex(functionFullPath, ".")+1:]
        if strings.HasPrefix(functionName, "Test") ||
            strings.HasPrefix(functionName, "Benchmark") ||
            strings.HasPrefix(functionName, "Example") {
            return functionName, nil
        }
    }
}