test: add GetExperimentPostTotalCountByCustomFilterUseCaseTest test code

src/test/kotlin/com/dobby/backend/application/usecase/experiment/GetExperimentPostTotalCountByCustomFilterUseCaseTest.kt

@@ -0,0 +1,56 @@
+package com.dobby.backend.application.usecase.experiment
+
+import com.dobby.backend.domain.gateway.experiment.ExperimentPostGateway
+import com.dobby.backend.infrastructure.database.entity.enums.MatchType
+import com.dobby.backend.infrastructure.database.entity.enums.experiment.RecruitStatus
+import io.kotest.core.spec.style.BehaviorSpec
+import io.kotest.matchers.shouldBe
+import io.mockk.every
+import io.mockk.mockk
+
+class GetExperimentPostTotalCountByCustomFilterUseCaseTest : BehaviorSpec({
+    val experimentPostGateway = mockk<ExperimentPostGateway>()
+    val getExperimentPostTotalCountByCustomFilterUseCase = GetExperimentPostTotalCountByCustomFilterUseCase(experimentPostGateway)
+
+    given("유효한 필터 조건이 주어졌을 때") {
+        val input = GetExperimentPostTotalCountByCustomFilterUseCase.Input(
+            matchType = MatchType.ALL,
+            studyTarget = null,
+            locationTarget = null,
+            recruitStatus = RecruitStatus.ALL
+        )
+
+        every {
+            experimentPostGateway.countExperimentPostsByCustomFilter(any())
+        } returns 10
+
+        `when`("execute가 호출되면") {
+            val result = getExperimentPostTotalCountByCustomFilterUseCase.execute(input)
+
+            then("올바른 게시글 개수를 반환한다") {
+                result shouldBe 10
+            }
+        }
+    }
+
+    given("필터 조건에 맞는 게시글이 없을 때") {
+        val input = GetExperimentPostTotalCountByCustomFilterUseCase.Input(
+            matchType = MatchType.OFFLINE,
+            studyTarget = null,
+            locationTarget = null,
+            recruitStatus = RecruitStatus.OPEN
+        )
+
+        every {
+            experimentPostGateway.countExperimentPostsByCustomFilter(any())
+        } returns 0
+
+        `when`("execute가 호출되면") {
+            val result = getExperimentPostTotalCountByCustomFilterUseCase.execute(input)
+
+            then("게시글 개수가 0으로 반환된다") {
+                result shouldBe 0
+            }
+        }
+    }
+})