write-test-case

name	write-test-case
description	Guide how to write test cases in this project by first analyzing the target class to decide which test pattern, base class, and test utilities to use. Activate when user asks to write tests, add test coverage, or create test cases for any class.

Write Test Case

Overview

This project is an IntelliJ IDEA plugin (EasyAPI). Tests use JUnit 4 + Mockito/Mockito-Kotlin + IntelliJ Platform Test Framework. Before writing any test, analyze the target class to pick the right pattern.

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Step 1 — Analyze the Target Class

Read the class under test and answer these questions:

Question	Answer leads to
Does it interact with PSI (PsiClass, PsiMethod, PsiField)?	IDE fixture pattern
Does it need a real IntelliJ Project object?	IDE fixture pattern
Does it export/format API endpoints?	IDE fixture + ResultLoader pattern
Is it a pure utility / data class with no IDE dependency?	Simple unit test pattern
Is it an AnAction subclass?	Action test pattern (extends IDE fixture)
Is it testing that multiple implementations share the same interface?	Parity test pattern

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Principle — Test Behavior, Not Implementation

Never test private methods via reflection. Private methods are implementation details. Tests should verify what a class does, not how it does it internally.

If you feel the urge to test a private method directly, treat it as a signal:

• The class is doing too much — extract the logic into a new class with a public interface, then test that class directly.
• Your public tests don't cover enough paths — add more test cases that exercise the private logic through the public API.

Reflection-based tests are brittle: they break on renames, bypass access modifiers intentionally, and make refactoring painful without adding real confidence.

The only meaningful exception is legacy code you genuinely cannot refactor. Even then, prefer extracting over reflecting.

Rule: if a private method is worth testing, it's worth making testable — either by testing it through the public API that calls it, or by extracting it into its own class.

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Step 2 — Choose the Right Pattern

Pattern A — Simple Unit Test

When: Pure utility, data model, formatter with no IntelliJ platform dependency, or any class with no IDE dependency.

Base: None (plain JUnit 4 class) Annotations: @Test, @Before, @After Mocking: mock<T>() from mockito-kotlin

import org.junit.Assert.*
import org.junit.Test

class MyServiceTest {

    @Test
    fun testSomeBehavior() {
        val result = MyService.doSomething("input")
        assertEquals("expected", result)
    }
}

Real examples: GsonUtilsTest, HttpModelsTest, CurlFormatterTest

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Pattern B — IDE Fixture Test (PSI / Project-aware)

When: Class needs a real Project, reads PSI elements, or is a project-level service.

Base: EasyApiLightCodeInsightFixtureTestCase Key methods available:

• loadFile(path) — loads a Java file from src/test/resources/ into the fixture project
• loadFile(path, content) — loads inline Java source
• findClass(qualifiedName) — finds a PsiClass by FQN
• findMethod(psiClass, name) — finds a method on a class
• waitForClass(qualifiedName, timeoutMs) — polls until a class is indexed (use when findClass returns null due to async indexing)
• loadJDKClass(fqn) — loads a JDK class stub into the fixture (needed for collection types, etc.)
• loadSource(clazz) — loads a class from source into the fixture
• runTest { } — runs a suspend block inside runBlocking
• settingBinder — property to access/modify test settings (via SettingBinder.getInstance(project))
• createConfigReader() — override to supply custom config rules

Test method naming: use fun test...() (no @Test annotation — JUnit 3 style inherited from LightJavaCodeInsightFixtureTestCase)

import com.itangcent.easyapi.testFramework.EasyApiLightCodeInsightFixtureTestCase
import com.itangcent.easyapi.testFramework.TestConfigReader

class MyExporterTest : EasyApiLightCodeInsightFixtureTestCase() {

    private lateinit var exporter: MyExporter

    override fun setUp() {
        super.setUp()
        loadTestFiles()
        exporter = MyExporter.getInstance(project) // or MyExporter(project)
    }

    // Override to supply config rules for this test class
    override fun createConfigReader() = TestConfigReader.empty(project)

    private fun loadTestFiles() {
        loadFile("spring/RequestMapping.java")
        loadFile("spring/GetMapping.java")
        loadFile("spring/RestController.java")
        loadFile("model/UserInfo.java")
        loadFile("api/UserCtrl.java")
    }

    fun testExportReturnsEndpoints() = runTest {
        val psiClass = findClass("com.itangcent.api.UserCtrl")
        assertNotNull(psiClass)
        val endpoints = exporter.export(psiClass!!)
        assertTrue(endpoints.isNotEmpty())
    }
}

Real examples: ExportOrchestratorTest, ApiDashboardServiceTest, DefaultConfigReaderTest, EndToEndExportTest

Important — Same-Package Import Requirement: In the IntelliJ PSI test fixture environment, all classes referenced by a Java file must be explicitly imported, even if they are in the same package. Without proper imports, the PSI will treat unresolved type references as UnresolvedType. For example, if UserController.java uses OrderedDTO from the same package, it must include import com.itangcent.jackson.OrderedDTO; even though they share the same package declaration.

Important — Async PSI Indexing: After loadFile(), findClass() may return null because the PSI index updates asynchronously. Use waitForClass(qualifiedName) which polls until the class is resolvable, instead of relying on a fixed delay().

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Pattern C — ResultLoader (snapshot / golden-file) Test

When: The output is a large formatted string (Markdown, Postman JSON, curl commands) that should be compared against a saved expected result.

Base: EasyApiLightCodeInsightFixtureTestCase Utility: ResultLoader

How it works:

1. Run the test once to produce actual output.
2. Save the output to src/test/resources/result/{FullyQualifiedTestClass}.{optionalName}.txt.
3. In the test, compare with ResultLoader.load() or ResultLoader.load("name").

File naming convention:

• Default: com.itangcent.easyapi.exporter.MyFormatterTest.txt
• Named: com.itangcent.easyapi.exporter.MyFormatterTest.testParseRequests.txt
• Inner classes: $ is replaced by . (e.g., MyTest.InnerTest → MyTest.InnerTest.txt)

import com.itangcent.easyapi.testFramework.EasyApiLightCodeInsightFixtureTestCase
import com.itangcent.easyapi.testFramework.ResultLoader

class MyFormatterTest : EasyApiLightCodeInsightFixtureTestCase() {

    fun testFormatOutput() = runTest {
        val endpoints = ApiFixtures.createSampleEndpoints()
        val result = MyFormatter().format(endpoints, "Test API")

        // Compare against saved golden file
        assertEquals(ResultLoader.load("testFormatOutput"), result.trimEnd())
    }
}

Real examples: PostmanFormatterTest, CurlFormatterTest

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⚠️ Cross-platform line endings — the golden-file parity trap

The pitfall. Code under test typically emits literal \n, but a golden file checked out on a Windows CI runner (default core.autocrlf=true) becomes \r\n on disk. A byte-for-byte assertEquals then fails on Windows only — passing on Linux/macOS, hiding the bug until a Windows CI run.

Always read golden/expected resources through the test framework, never via File.readText() / Paths.readText(). Two helpers, both in com.itangcent.easyapi.testFramework:

Helper	When to use	Normalization
ResultLoader.load() / load("name")	Snapshot/golden test where trailing whitespace doesn't matter (default choice)	CRLF→LF + trimEnd()
ResourceLoader.read("/path/in/resources")	Same, when you control the resource path explicitly	CRLF→LF + trimEnd()
ResourceLoader.readRaw("/path/in/resources")	Byte-for-byte parity gate where trailing whitespace MUST be preserved (e.g. MarkdownTemplateParityTest)	CRLF→LF only

Both read and readRaw collapse CRLF→LF; the difference is whether trailing whitespace is trimmed. Use readRaw only when the test's contract is strict byte equality — for everything else, prefer ResultLoader/read.

When writing a new parity/golden test, ask: "Does my actual value carry meaningful trailing whitespace?" If yes → ResourceLoader.readRaw. If no → ResultLoader.load (which already calls ResourceLoader.read).

The repo also ships a .gitattributes forcing eol=lf for text files, so golden files committed with LF stay LF on Windows checkouts. Do not weaken this.

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Pattern D — Action Test

When: Testing an AnAction subclass.

Base: EasyApiLightCodeInsightFixtureTestCase (provides a real Project) Key: Use AnActionEvent.createFromDataContext to construct events with the test project.

import com.intellij.openapi.actionSystem.AnActionEvent
import com.intellij.openapi.actionSystem.Presentation
import com.itangcent.easyapi.testFramework.EasyApiLightCodeInsightFixtureTestCase
import org.junit.Assert.*

class MyActionTest : EasyApiLightCodeInsightFixtureTestCase() {

    private lateinit var action: MyAction

    override fun setUp() {
        super.setUp()
        action = MyAction()
    }

    fun testUpdateWithProject() {
        val presentation = Presentation()
        val event = AnActionEvent.createFromDataContext(
            "test",
            presentation
        ) { project }

        action.update(event)

        assertTrue("Action should be enabled with project", event.presentation.isEnabled)
    }

    fun testUpdateWithoutProject() {
        val presentation = Presentation()
        val event = AnActionEvent.createFromDataContext(
            "test",
            presentation
        ) { null }

        action.update(event)

        assertFalse("Action should be disabled without project", event.presentation.isEnabled)
    }
}

Real examples: ExportApiActionTest, ChannelExportActionTest, ApiCallActionTest, EasyApiActionTest

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Pattern E — Parity / Contract Test

When: Verifying that multiple implementations of the same interface all exist and behave consistently.

Base: EasyApiLightCodeInsightFixtureTestCase

import com.itangcent.easyapi.exporter.feign.FeignClassExporter
import com.itangcent.easyapi.exporter.jaxrs.JaxRsClassExporter
import com.itangcent.easyapi.exporter.springmvc.SpringMvcClassExporter
import com.itangcent.easyapi.testFramework.EasyApiLightCodeInsightFixtureTestCase
import com.itangcent.easyapi.testFramework.TestConfigReader
import org.junit.Assert.*

class ExporterParityTest : EasyApiLightCodeInsightFixtureTestCase() {

    override fun createConfigReader() = TestConfigReader.empty(project)

    fun testAllExportersExist() = runTest {
        assertNotNull(SpringMvcClassExporter(project))
        assertNotNull(FeignClassExporter(project))
        assertNotNull(JaxRsClassExporter(project))
    }
}

Real examples: FeatureParityTest, FormatterParityTest, SettingBinderParityTest

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Step 3 — Use the Right Test Utilities

ApiFixtures — Pre-built test data

Use when you need ApiEndpoint, Settings, or common endpoint lists without PSI.

val endpoint = ApiFixtures.createEndpoint(name = "getUser", path = "/api/users/{id}")
val getEndpoint = ApiFixtures.createGetEndpoint(name = "getUser", path = "/api/users/{id}")
val postEndpoint = ApiFixtures.createPostEndpoint()  // POST with body params
val uploadEndpoint = ApiFixtures.createFileUploadEndpoint()
val endpoints = ApiFixtures.createSampleEndpoints()  // 5 CRUD endpoints
val settings = ApiFixtures.createSettings()          // settings with test token

TestConfigReader — Fake config rules

Use to inject .easy.api.config-style rules without touching the filesystem. All factory methods require project as the first parameter.

// No config
TestConfigReader.empty(project)

// From key=value pairs
TestConfigReader.fromRules(
    project,
    "method.return.main.status" to "200",
    "ignore" to "@Deprecated"
)

// From config file text
TestConfigReader.fromConfigText(
    project,
    """
    method.return.main.status=200
    ignore=@Deprecated
    """.trimIndent()
)

// From a map
TestConfigReader.fromMap(project, mapOf("key" to "value"))

SettingBinder.update { } — Mutate settings in tests

The settingBinder property in EasyApiLightCodeInsightFixtureTestCase provides access to settings. Use the update extension function to modify settings:

// In setUp() — applies to all tests in the class
override fun setUp() {
    super.setUp()
    settingBinder.update {
        postmanToken = "my-token"
        feignEnable = true
        httpTimeOut = 5000
    }
}

// In a test method — applies only to that test
fun testSomething() {
    settingBinder.update {
        postmanToken = "custom-token"
    }
    // test code
}

ProjectWrapper — Replace project services

Use when you need to swap out a specific project service without rebuilding the whole context.

import com.itangcent.easyapi.testFramework.wrap

val wrappedProject = wrap(project) {
    replaceService(MyProjectService::class, FakeMyProjectService())
}

Alternatively, use project.registerServiceInstance(...) directly in setUp():

override fun setUp() {
    super.setUp()
    project.registerServiceInstance(
        serviceInterface = MyService::class.java,
        instance = MockMyService()
    )
}

ResultLoader — Load golden-file expected output

ResultLoader.load()              // loads {ClassName}.txt
ResultLoader.load("name")        // loads {ClassName}.name.txt
ResultLoader.loadOrNull("name")  // returns null if file missing

---

Step 4 — Test Resource Files

Java source files used as PSI fixtures live in src/test/resources/. Common ones:

Path	Contents
spring/	Spring MVC annotations (GetMapping, PostMapping, PutMapping, DeleteMapping, RequestMapping, RequestParam, PathVariable, RequestBody, etc.)
api/UserCtrl.java	Sample Spring REST controller
model/UserInfo.java, model/Result.java	Common model classes
constant/UserType.java	Enum example
jaxrs/	JAX-RS annotations
feign/	Feign annotations
validation/	javax.validation annotations
jdk/	JDK class stubs for the light fixture

Always load the minimum set of files needed. Load Spring annotation stubs before loading controllers that use them.

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Step 5 — Decision Flowchart

Target class uses PSI / Project?
├── YES → Pattern B (EasyApiLightCodeInsightFixtureTestCase)
│         Output is a large formatted string?
│         └── YES → also use Pattern C (ResultLoader)
└── NO
    ├── Is an AnAction subclass?
    │   └── YES → Pattern D (Action Test — still extends IDE fixture for real Project)
    ├── Testing multiple implementations for parity?
    │   └── YES → Pattern E (Parity Test)
    └── Pure utility / data class / formatter?
        └── YES → Pattern A (Simple Unit Test)

---

Step 6 — Naming & Location Conventions

• Test class: src/test/kotlin/com/itangcent/easyapi/{package}/{ClassName}Test.kt
• Golden files: src/test/resources/result/{FQN}.{name}.txt
• Test resources: src/test/resources/{category}/
• Method names: fun testSomeBehavior() (no @Test in IDE fixture tests — JUnit 3 style), @Test fun testSomeBehavior() in plain JUnit 4 tests
• Assertion messages: always include a descriptive message as the first argument, e.g. assertEquals("Should return same instance", a, b)

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Step 7 — Running Tests

# Run all tests
./gradlew test

# Run a specific test class
./gradlew test --tests "com.itangcent.easyapi.exporter.ExportOrchestratorTest"

# Run a specific test method
./gradlew test --tests "com.itangcent.easyapi.exporter.ExportOrchestratorTest.testGetInstanceReturnsSameInstance"