diff --git a/build.gradle.kts b/build.gradle.kts
index 22e7087..0d8dffd 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -50,7 +50,7 @@ dependencies {
     implementation("org.springframework.boot:spring-boot-devtools:${springBootVersion}")
 
     testImplementation("com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0")
-    testImplementation("io.mockk:mockk:1.12.0")
+    testImplementation("io.mockk:mockk:1.12.1")
     testImplementation("org.jetbrains.kotlin:kotlin-test:${kotlinVersion}")
     testImplementation("org.mockito:mockito-inline:3.11.2")
     testImplementation("org.springframework:spring-test:5.3.13")
@@ -68,8 +68,8 @@ springBoot {
 }
 
 java {
-    sourceCompatibility = JavaVersion.VERSION_11
-    targetCompatibility = JavaVersion.VERSION_11
+    sourceCompatibility = JavaVersion.VERSION_17
+    targetCompatibility = JavaVersion.VERSION_17
 }
 
 sourceSets {
@@ -83,15 +83,18 @@ sourceSets {
 }
 
 tasks.test {
+    useJUnitPlatform()
+
+    jvmArgs("-XX:+ShowCodeDetailsInExceptionMessages")
+    testLogging {
+        events("skipped", "failed")
+        setExceptionFormat("full")
+    }
+
     reports {
         junitXml.required.set(true)
         html.required.set(false)
     }
-
-    useJUnitPlatform()
-    testLogging {
-        events("skipped", "failed")
-    }
 }
 
 tasks.withType<JavaCompile>() {
diff --git a/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileExistCache.kt b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileExistCache.kt
new file mode 100644
index 0000000..46abd2e
--- /dev/null
+++ b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileExistCache.kt
@@ -0,0 +1,23 @@
+package dev.fyloz.colorrecipesexplorer.service.files
+
+import dev.fyloz.colorrecipesexplorer.utils.FilePath
+
+class FileExistCache {
+    private val map = hashMapOf<FilePath, Boolean>()
+
+    operator fun contains(path: FilePath) =
+        path in map
+
+    fun exists(path: FilePath) =
+        map[path] ?: false
+
+    fun set(path: FilePath, exists: Boolean) {
+        map[path] = exists
+    }
+
+    fun setExists(path: FilePath) =
+        set(path, true)
+
+    fun setDoesNotExists(path: FilePath) =
+        set(path, false)
+}
\ No newline at end of file
diff --git a/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileService.kt b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileService.kt
index 4136ebe..683cb74 100644
--- a/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileService.kt
+++ b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileService.kt
@@ -2,6 +2,9 @@ package dev.fyloz.colorrecipesexplorer.service.files
 
 import dev.fyloz.colorrecipesexplorer.config.properties.CreProperties
 import dev.fyloz.colorrecipesexplorer.exception.RestException
+import dev.fyloz.colorrecipesexplorer.utils.FilePath
+import dev.fyloz.colorrecipesexplorer.utils.WrappedFile
+import dev.fyloz.colorrecipesexplorer.utils.withFileAt
 import org.slf4j.Logger
 import org.springframework.core.io.ByteArrayResource
 import org.springframework.core.io.Resource
@@ -49,8 +52,17 @@ class FileServiceImpl(
     private val creProperties: CreProperties,
     private val logger: Logger
 ) : WriteableFileService {
-    override fun exists(path: String) = withFileAt(path.fullPath()) {
-        this.exists() && this.isFile
+    private val existsCache = FileExistCache()
+
+    override fun exists(path: String): Boolean {
+        val fullPath = path.fullPath()
+        return if (fullPath in existsCache) {
+            existsCache.exists(fullPath)
+        } else {
+            withFileAt(fullPath) {
+                this.exists() && this.isFile
+            }
+        }
     }
 
     override fun read(path: String) = ByteArrayResource(
@@ -70,6 +82,7 @@ class FileServiceImpl(
             try {
                 withFileAt(fullPath) {
                     this.create()
+                    existsCache.setExists(fullPath)
                 }
             } catch (ex: IOException) {
                 FileCreateException(path).logAndThrow(ex, logger)
@@ -89,9 +102,12 @@ class FileServiceImpl(
 
     override fun delete(path: String) {
         try {
-            withFileAt(path.fullPath()) {
+            val fullPath = path.fullPath()
+            withFileAt(fullPath) {
                 if (!exists(path)) throw FileNotFoundException(path)
-                !this.delete()
+
+                this.delete()
+                existsCache.setDoesNotExists(fullPath)
             }
         } catch (ex: IOException) {
             FileDeleteException(path).logAndThrow(ex, logger)
@@ -106,7 +122,7 @@ class FileServiceImpl(
         return FilePath("${creProperties.dataDirectory}/$this")
     }
 
-    private fun prepareWrite(path: String, overwrite: Boolean, op: File.() -> Unit) {
+    private fun prepareWrite(path: String, overwrite: Boolean, op: WrappedFile.() -> Unit) {
         val fullPath = path.fullPath()
 
         if (exists(path)) {
@@ -123,15 +139,6 @@ class FileServiceImpl(
             FileWriteException(path).logAndThrow(ex, logger)
         }
     }
-
-    /** Runs the given [block] in the context of a file with the given [fullPath]. */
-    private fun <T> withFileAt(fullPath: FilePath, block: File.() -> T) =
-        fullPath.file.block()
-}
-
-data class FilePath(val path: String) {
-    val file: File
-        get() = File(path)
 }
 
 /** Shortcut to create a file and its parent directories. */
diff --git a/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileService.kt b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileService.kt
index be9ba6e..d33bc9e 100644
--- a/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileService.kt
+++ b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileService.kt
@@ -1,5 +1,6 @@
 package dev.fyloz.colorrecipesexplorer.service.files
 
+import dev.fyloz.colorrecipesexplorer.utils.FilePath
 import org.springframework.core.io.Resource
 import org.springframework.core.io.ResourceLoader
 import org.springframework.stereotype.Service
diff --git a/src/main/kotlin/dev/fyloz/colorrecipesexplorer/utils/Files.kt b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/utils/Files.kt
new file mode 100644
index 0000000..8e08f4f
--- /dev/null
+++ b/src/main/kotlin/dev/fyloz/colorrecipesexplorer/utils/Files.kt
@@ -0,0 +1,44 @@
+package dev.fyloz.colorrecipesexplorer.utils
+
+import dev.fyloz.colorrecipesexplorer.service.files.create
+import java.io.File
+import java.nio.file.Path
+
+/** Mockable file wrapper, to prevent issues when mocking [java.io.File]. */
+class WrappedFile(val file: File) {
+    val isFile: Boolean
+        get() = file.isFile
+
+    fun toPath(): Path =
+        file.toPath()
+
+    fun exists() =
+        file.exists()
+
+    fun readBytes() =
+        file.readBytes()
+
+    fun writeBytes(array: ByteArray) =
+        file.writeBytes(array)
+
+    fun create() =
+        file.create()
+
+    fun delete(): Boolean =
+        file.delete()
+
+    companion object {
+        fun from(path: String) =
+            WrappedFile(File(path))
+
+        fun from(path: FilePath) =
+            from(path.path)
+    }
+}
+
+@JvmInline
+value class FilePath(val path: String)
+
+/** Runs the given [block] in the context of a file with the given [fullPath]. */
+fun <T> withFileAt(fullPath: FilePath, block: WrappedFile.() -> T) =
+    WrappedFile.from(fullPath).block()
\ No newline at end of file
diff --git a/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileServiceTest.kt b/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileServiceTest.kt
index 936bf47..a68a93d 100644
--- a/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileServiceTest.kt
+++ b/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/FileServiceTest.kt
@@ -1,6 +1,7 @@
 package dev.fyloz.colorrecipesexplorer.service.files
 
 import dev.fyloz.colorrecipesexplorer.config.properties.CreProperties
+import dev.fyloz.colorrecipesexplorer.utils.WrappedFile
 import io.mockk.*
 import org.junit.jupiter.api.AfterEach
 import org.junit.jupiter.api.Test
@@ -24,20 +25,18 @@ private class FileServiceTestContext {
     val fileService = spyk(FileServiceImpl(creProperties, mockk {
         every { error(any(), any<Exception>()) } just Runs
     }))
-    val mockFile = mockk<File> {
-        every { path } returns mockFilePath
+    val mockFile = mockk<WrappedFile> {
+        every { file } returns mockk()
         every { exists() } returns true
         every { isFile } returns true
         every { toPath() } returns mockFilePathPath
     }
-    val mockFileFullPath = spyk(FilePath("${creProperties.dataDirectory}/$mockFilePath")) {
-        every { file } returns mockFile
-
-        with(fileService) {
-            every { mockFilePath.fullPath() } returns this@spyk
-        }
-    }
     val mockMultipartFile = spyk(MockMultipartFile(mockFilePath, mockFileData))
+
+    init {
+        mockkObject(WrappedFile.Companion)
+        every { WrappedFile.from(any<String>()) } returns mockFile
+    }
 }
 
 class FileServiceTest {
diff --git a/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileServiceTest.kt b/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileServiceTest.kt
index 5c0d6ff..9aafde9 100644
--- a/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileServiceTest.kt
+++ b/src/test/kotlin/dev/fyloz/colorrecipesexplorer/service/files/ResourceFileServiceTest.kt
@@ -1,5 +1,6 @@
 package dev.fyloz.colorrecipesexplorer.service.files
 
+import dev.fyloz.colorrecipesexplorer.utils.FilePath
 import io.mockk.clearAllMocks
 import io.mockk.every
 import io.mockk.mockk