diff --git a/src/functionalTest/groovy/com/autonomousapps/AdviceHelper.groovy b/src/functionalTest/groovy/com/autonomousapps/AdviceHelper.groovy
index 68515a5de..67218a513 100644
--- a/src/functionalTest/groovy/com/autonomousapps/AdviceHelper.groovy
+++ b/src/functionalTest/groovy/com/autonomousapps/AdviceHelper.groovy
@@ -51,8 +51,9 @@ final class AdviceHelper {
     return new ProjectCoordinates(projectPath, defaultGVI(capability), buildPath)
   }
 
-  static Coordinates includedBuildCoordinates(String identifier, ProjectCoordinates resolvedProject,
-    String capability = null) {
+  static Coordinates includedBuildCoordinates(
+    String identifier, ProjectCoordinates resolvedProject, String capability = null
+  ) {
     return new IncludedBuildCoordinates(identifier, resolvedProject, defaultGVI(capability))
   }
 
@@ -76,8 +77,9 @@ final class AdviceHelper {
     return projectAdvice(projectPath, advice, pluginAdvice, false)
   }
 
-  static ProjectAdvice projectAdvice(String projectPath, Set<Advice> advice, Set<PluginAdvice> pluginAdvice,
-    boolean shouldFail) {
+  static ProjectAdvice projectAdvice(
+    String projectPath, Set<Advice> advice, Set<PluginAdvice> pluginAdvice, boolean shouldFail
+  ) {
     return projectAdvice(projectPath, advice, pluginAdvice, [] as Set<ModuleAdvice>, shouldFail)
   }
 
diff --git a/src/functionalTest/groovy/com/autonomousapps/AdviceStrategy.groovy b/src/functionalTest/groovy/com/autonomousapps/AdviceStrategy.groovy
index 9b24d31fb..c95cfa6ec 100644
--- a/src/functionalTest/groovy/com/autonomousapps/AdviceStrategy.groovy
+++ b/src/functionalTest/groovy/com/autonomousapps/AdviceStrategy.groovy
@@ -2,18 +2,14 @@
 // SPDX-License-Identifier: Apache-2.0
 package com.autonomousapps
 
-
 import com.autonomousapps.internal.OutputPathsKt
 import com.autonomousapps.internal.utils.MoshiUtils
 import com.autonomousapps.kit.GradleProject
-import com.autonomousapps.kit.utils.Files
-import com.autonomousapps.model.Advice
 import com.autonomousapps.model.BuildHealth
 import com.autonomousapps.model.ProjectAdvice
 import com.squareup.moshi.Types
 
 abstract class AdviceStrategy {
-  abstract List<Advice> actualAdviceForFirstSubproject(GradleProject gradleProject)
 
   abstract def actualBuildHealth(GradleProject gradleProject)
 
@@ -41,7 +37,8 @@ abstract class AdviceStrategy {
 
     @Override
     Map<String, Set<String>> getDuplicateDependenciesReport(GradleProject gradleProject) {
-      def json = Files.resolveFromRoot(gradleProject, OutputPathsKt.getDuplicateDependenciesReport()).text.trim()
+      def json = gradleProject.singleArtifact(':', OutputPathsKt.getDuplicateDependenciesReport())
+        .asPath.text.trim()
       def set = Types.newParameterizedType(Set, String)
       def map = Types.newParameterizedType(Map, String, set)
       def adapter = MoshiUtils.MOSHI.<Map<String, Set<String>>> adapter(map)
@@ -50,25 +47,20 @@ abstract class AdviceStrategy {
 
     @Override
     List<String> getResolvedDependenciesReport(GradleProject gradleProject, String projectPath) {
-      File report = Files.resolveFromName(gradleProject, projectPath, OutputPathsKt.getResolvedDependenciesReport())
-      return report.text.trim().readLines()
+      def report = gradleProject.singleArtifact(projectPath, OutputPathsKt.getResolvedDependenciesReport())
+      return report.asPath.text.trim().readLines()
     }
 
     @Override
     def actualBuildHealth(GradleProject gradleProject) {
-      File buildHealth = Files.resolveFromRoot(gradleProject, OutputPathsKt.getFinalAdvicePathV2())
-      return fromAllProjectAdviceJson(buildHealth.text)
+      def buildHealth = gradleProject.singleArtifact(':', OutputPathsKt.getFinalAdvicePathV2())
+      return fromAllProjectAdviceJson(buildHealth.asPath.text)
     }
 
     @Override
     def actualComprehensiveAdviceForProject(GradleProject gradleProject, String projectName) {
-      File advice = Files.resolveFromName(gradleProject, projectName, OutputPathsKt.getAggregateAdvicePathV2())
-      return fromProjectAdvice(advice.text)
-    }
-
-    @Override
-    List<Advice> actualAdviceForFirstSubproject(GradleProject gradleProject) {
-      throw new IllegalStateException("Not yet implemented")
+      def advice = gradleProject.singleArtifact(projectName, OutputPathsKt.getAggregateAdvicePathV2())
+      return fromProjectAdvice(advice.asPath.text)
     }
   }
 }
diff --git a/testkit/gradle-testkit-support/build.gradle.kts b/testkit/gradle-testkit-support/build.gradle.kts
index 7ead4a9a9..baa14ac85 100644
--- a/testkit/gradle-testkit-support/build.gradle.kts
+++ b/testkit/gradle-testkit-support/build.gradle.kts
@@ -42,10 +42,10 @@ dependencies {
   api(platform(libs.kotlin.bom))
   api(gradleTestKit())
 
-  implementation(libs.truth)
-
   testImplementation(platform(libs.junit.bom))
   testImplementation(libs.junit.api)
+  testImplementation(libs.truth)
+
   testRuntimeOnly(libs.junit.engine)
 
   dokkaHtmlPlugin(libs.kotlin.dokka)
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/GradleProject.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/GradleProject.kt
index ea5ce93da..075e3bab9 100644
--- a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/GradleProject.kt
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/GradleProject.kt
@@ -7,11 +7,17 @@ import com.autonomousapps.kit.android.AndroidColorRes
 import com.autonomousapps.kit.android.AndroidManifest
 import com.autonomousapps.kit.android.AndroidStyleRes
 import com.autonomousapps.kit.android.AndroidSubproject
+import com.autonomousapps.kit.artifacts.BuildArtifact
+import com.autonomousapps.kit.artifacts.toBuildArtifact
 import com.autonomousapps.kit.gradle.BuildScript
 import com.autonomousapps.kit.gradle.GradleProperties
 import com.autonomousapps.kit.gradle.SettingsScript
+import com.autonomousapps.kit.internal.ensurePrefix
+import com.autonomousapps.kit.utils.buildPathForName
 import java.io.File
+import java.nio.file.Files
 import java.nio.file.Path
+import kotlin.io.path.exists
 
 /**
  * A Gradle project consists of:
@@ -60,9 +66,7 @@ public class GradleProject(
   }
 
   /** Use ":" for the root project. */
-  public fun projectDir(projectName: String): Path {
-    return projectDir(forName(projectName))
-  }
+  public fun projectDir(projectName: String): Path = projectDir(forName(projectName))
 
   /** Use [rootProject] for the root project. */
   public fun projectDir(project: Subproject): Path {
@@ -72,14 +76,18 @@ public class GradleProject(
     return rootDir.toPath().resolve("${project.includedBuild?.let { "$it/" } ?: ""}${project.name.replace(":", "/")}/")
   }
 
-  /** Use ":" for the root project. */
-  public fun buildDir(projectName: String): Path {
-    return buildDir(forName(projectName))
+  /**
+   * Provides access to a build directory for one of the projects in your fixture. Use ":" for the root project.
+   */
+  @JvmOverloads
+  public fun buildDir(projectName: String, buildDirName: String = "build"): Path {
+    return buildDir(project = forName(projectName), buildDirName = buildDirName)
   }
 
   /** Use [rootProject] for the root project. */
-  public fun buildDir(project: Subproject): Path {
-    return projectDir(project).resolve("build/")
+  @JvmOverloads
+  public fun buildDir(project: Subproject, buildDirName: String = "build"): Path {
+    return projectDir(project).resolve("${buildDirName}/")
   }
 
   public fun findIncludedBuild(path: String): GradleProject? {
@@ -103,13 +111,68 @@ public class GradleProject(
     }
   }
 
+  /**
+   * Returns the single artifact at [relativePath] from the build directory of project [projectName], failing if no such
+   * artifact exists. Uses "build" as the build directory name by default.
+   */
+  @JvmOverloads
+  public fun singleArtifact(
+    projectName: String,
+    relativePath: String,
+    buildDirName: String = "build",
+  ): BuildArtifact {
+    val artifact = buildPathForName(path = projectName, buildDirName = buildDirName).resolve(relativePath)
+    check(artifact.exists()) { "No artifact with path '$artifact'" }
+    return BuildArtifact(artifact)
+  }
+
+  /**
+   * Returns the single artifact at [relativePath] from the build directory of project [projectName], failing if no such
+   * artifact exists. An alias for [singleArtifact]. Uses "build" as the build directory name by default.
+   */
+  @JvmOverloads
+  public fun getArtifact(projectName: String, relativePath: String, buildDirName: String = "build"): BuildArtifact {
+    return singleArtifact(projectName = projectName, relativePath = relativePath, buildDirName = buildDirName)
+  }
+
+  /**
+   * Returns the single artifact at [relativePath] from the build directory of project [projectName], or `null` if no such
+   * artifact exists. Uses "build" as the build directory name by default.
+   */
+  @JvmOverloads
+  public fun findArtifact(
+    projectName: String,
+    relativePath: String,
+    buildDirName: String = "build",
+  ): BuildArtifact? {
+    val artifact = buildPathForName(path = projectName, buildDirName = buildDirName).resolve(relativePath)
+    return if (artifact.exists()) {
+      artifact.toBuildArtifact()
+    } else {
+      null
+    }
+  }
+
+  /**
+   * Returns the directory at [relativePath] from the build directory of project [projectName], failing if no such
+   * directory exists, or if it is not a directory. Returned [Path] may be empty. Uses "build" as the build directory name
+   * by default.
+   */
+  @JvmOverloads
+  public fun artifacts(projectName: String, relativePath: String, buildDirName: String = "build"): BuildArtifact {
+    val dir = buildPathForName(path = projectName, buildDirName = buildDirName).resolve(relativePath)
+    check(dir.exists()) { "No directory with path '$dir'" }
+    check(Files.isDirectory(dir)) { "Expected directory, was '$dir'" }
+    return dir.toBuildArtifact()
+  }
+
   private fun forName(projectName: String): Subproject {
     if (projectName == ":") {
       return rootProject
     }
 
-    return subprojects.find { it.name == projectName }
-      ?: throw IllegalStateException("No subproject with name $projectName")
+    return subprojects.find { it.name.ensurePrefix() == projectName.ensurePrefix() }
+      ?: throw IllegalStateException("No subproject with name '$projectName'")
   }
 
   public class Builder @JvmOverloads constructor(
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/Subproject.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/Subproject.kt
index eae004162..50c606d96 100644
--- a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/Subproject.kt
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/Subproject.kt
@@ -23,9 +23,7 @@ public open class Subproject(
   public val variant: String,
 ) {
 
-  /**
-   * We only care about the subproject's name for equality comparisons and hashing.
-   */
+  /** We only care about the subproject's name for equality comparisons and hashing. */
   override fun equals(other: Any?): Boolean {
     if (this === other) return true
     if (other !is Subproject) return false
@@ -34,9 +32,7 @@ public open class Subproject(
     return true
   }
 
-  /**
-   * We only care about the subproject's name for equality comparisons and hashing.
-   */
+  /** We only care about the subproject's name for equality comparisons and hashing. */
   override fun hashCode(): Int = name.hashCode()
 
   public class Builder {
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/artifacts/BuildArtifact.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/artifacts/BuildArtifact.kt
new file mode 100644
index 000000000..4cc3784c8
--- /dev/null
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/artifacts/BuildArtifact.kt
@@ -0,0 +1,33 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.artifacts
+
+import java.io.File
+import java.nio.file.Path
+import kotlin.io.path.*
+
+/**
+ * Essentially a wrapper around [path], with the intention to provide an expanded API eventually.
+ */
+public class BuildArtifact(private val path: Path) {
+
+  /**
+   * The [Path] represented by this build artifact.
+   */
+  public val asPath: Path get() = path
+
+  /**
+   * The [File] represented by this build artifact.
+   */
+  public val asFile: File get() = path.toFile()
+
+  public fun exists(): Boolean = path.exists()
+  public fun notExists(): Boolean = path.notExists()
+  public fun isRegularFile(): Boolean = path.isRegularFile()
+  public fun isDirectory(): Boolean = path.isDirectory()
+  public fun isSymbolicLink(): Boolean = path.isSymbolicLink()
+
+  public val extension: String get() = path.extension
+}
+
+internal fun Path.toBuildArtifact(): BuildArtifact = BuildArtifact(this)
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/artifacts/FileType.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/artifacts/FileType.kt
new file mode 100644
index 000000000..fecf0bb7e
--- /dev/null
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/artifacts/FileType.kt
@@ -0,0 +1,29 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.artifacts
+
+import java.nio.file.LinkOption
+import java.nio.file.Path
+import kotlin.io.path.isDirectory
+import kotlin.io.path.isRegularFile
+import kotlin.io.path.isSymbolicLink
+
+public enum class FileType(public val humanReadableName: String) {
+  REGULAR_FILE("regular file"),
+  DIRECTORY("directory"),
+  SYMLINK("symbolic link"),
+  UNKNOWN("unknown");
+
+  public companion object {
+    public fun from(buildArtifact: BuildArtifact, vararg options: LinkOption): FileType {
+      return from(buildArtifact.asPath, *options)
+    }
+
+    public fun from(path: Path, vararg options: LinkOption): FileType = when {
+      path.isRegularFile(*options) -> REGULAR_FILE
+      path.isDirectory(*options) -> DIRECTORY
+      path.isSymbolicLink() -> SYMLINK
+      else -> UNKNOWN
+    }
+  }
+}
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/BuildScript.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/BuildScript.kt
index 5284a5c24..ee829241f 100644
--- a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/BuildScript.kt
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/BuildScript.kt
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 package com.autonomousapps.kit.gradle
 
+import com.autonomousapps.kit.GradleProject
 import com.autonomousapps.kit.gradle.android.AndroidBlock
 import com.autonomousapps.kit.render.Scribe
 import org.intellij.lang.annotations.Language
@@ -19,6 +20,8 @@ public class BuildScript(
   public val java: Java? = null,
   public val kotlin: Kotlin? = null,
   public val additions: String = "",
+  private val usesGroovy: Boolean = false,
+  private val usesKotlin: Boolean = false,
 ) {
 
   private val groupVersion = GroupVersion(group = group, version = version)
@@ -59,6 +62,14 @@ public class BuildScript(
     kotlin?.let { k -> appendLine(scribe.use { s -> k.render(s) }) }
 
     if (additions.isNotBlank()) {
+      if (usesGroovy && scribe.dslKind != GradleProject.DslKind.GROOVY) {
+        error("You called withGroovy() but you're using Kotlin DSL")
+      }
+
+      if (usesKotlin && scribe.dslKind != GradleProject.DslKind.KOTLIN) {
+        error("You called withKotlin() but you're using Groovy DSL")
+      }
+
       appendLine(additions)
     }
 
@@ -80,8 +91,17 @@ public class BuildScript(
     public var kotlin: Kotlin? = null
     public var additions: String = ""
 
+    private var usesGroovy = false
+    private var usesKotlin = false
+
     public fun withGroovy(@Language("Groovy") script: String) {
       additions = script.trimIndent()
+      usesGroovy = true
+    }
+
+    public fun withKotlin(@Language("kt") script: String) {
+      additions = script.trimIndent()
+      usesKotlin = true
     }
 
     public fun dependencies(vararg dependencies: Dependency) {
@@ -120,7 +140,9 @@ public class BuildScript(
         dependencies = Dependencies(dependencies),
         java = java,
         kotlin = kotlin,
-        additions = additions
+        additions = additions,
+        usesGroovy = usesGroovy,
+        usesKotlin = usesKotlin,
       )
     }
   }
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/Dependency.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/Dependency.kt
index c83843a65..eb7a7815b 100644
--- a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/Dependency.kt
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/Dependency.kt
@@ -3,6 +3,7 @@
 package com.autonomousapps.kit.gradle
 
 import com.autonomousapps.kit.GradleProject.DslKind
+import com.autonomousapps.kit.internal.ensurePrefix
 import com.autonomousapps.kit.render.Element
 import com.autonomousapps.kit.render.Scribe
 
@@ -182,8 +183,6 @@ public class Dependency @JvmOverloads constructor(
       return Dependency(configuration, path.ensurePrefix(), capability = capability)
     }
 
-    private fun String.ensurePrefix(prefix: String = ":"): String = if (startsWith(prefix)) this else "$prefix$this"
-
     @JvmStatic
     public fun raw(configuration: String, dependency: String): Dependency {
       check(!dependency.contains(":")) { "Not meant for normal dependencies. Was '$dependency'." }
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/Files.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/files.kt
similarity index 94%
rename from testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/Files.kt
rename to testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/files.kt
index 3c5c3b08d..da1586e46 100644
--- a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/Files.kt
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/files.kt
@@ -5,6 +5,6 @@ package com.autonomousapps.kit.internal
 import java.io.File
 import java.nio.charset.Charset
 
-internal fun File.writeAny(any: Any, charset: Charset = Charsets.UTF_8): Unit {
+internal fun File.writeAny(any: Any, charset: Charset = Charsets.UTF_8) {
   writeBytes(any.toString().toByteArray(charset))
 }
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/strings.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/strings.kt
new file mode 100644
index 000000000..b8b71c03e
--- /dev/null
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/internal/strings.kt
@@ -0,0 +1,7 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.internal
+
+internal fun String.ensurePrefix(prefix: String = ":"): String {
+  return if (startsWith(prefix)) this else "$prefix$this"
+}
diff --git a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/utils/files.kt b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/utils/files.kt
index 904b9d669..ad876f92a 100644
--- a/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/utils/files.kt
+++ b/testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/utils/files.kt
@@ -5,24 +5,42 @@
 package com.autonomousapps.kit.utils
 
 import com.autonomousapps.kit.GradleProject
-import com.google.common.truth.Truth.assertWithMessage
+import com.autonomousapps.kit.internal.ensurePrefix
 import java.io.File
 import java.nio.file.Path
 
-/** Returns the path to the build dir of the root project. */
-public fun GradleProject.rootBuildPath(): Path = buildDir(":")
+/**
+ * Returns the path to the build directory of the root project. Uses "build" as the build directory name by default.
+ */
+@JvmOverloads
+public fun GradleProject.rootBuildPath(buildDirName: String = "build"): Path = buildDir(
+  projectName = ":",
+  buildDirName = buildDirName,
+)
 
-/** Returns the directory of the build dir of the root project. */
-public fun GradleProject.rootBuildDir(): File = rootBuildPath().toFile()
+/**
+ * Returns the directory of the build directory of the root project. Uses "build" as the build directory name by
+ * default.
+ */
+@JvmOverloads
+public fun GradleProject.rootBuildDir(buildDirName: String = "build"): File = rootBuildPath(buildDirName).toFile()
 
-/** Returns the file specified, relative to the root project. */
-public fun GradleProject.resolveFromRoot(relativePath: String): File {
-  return rootBuildPath().resolve(relativePath).toFile()
+/**
+ * Returns the file specified, relative to the build directory of the root project. Uses "build" as the build directory
+ * name by default.
+ */
+@Deprecated(
+  "Use singleArtifact",
+  replaceWith = ReplaceWith("singleArtifact(\":\", relativePath)")
+)
+@JvmOverloads
+public fun GradleProject.resolveFromRoot(relativePath: String, buildDirName: String = "build"): File {
+  return rootBuildPath(buildDirName).resolve(relativePath).toFile()
 }
 
 /** Returns the path to the build dir of the first subproject, asserting that there is only one. */
 public fun GradleProject.singleSubprojectBuildPath(): Path {
-  assertWithMessage("Expected only a single subproject").that(subprojects.size).isEqualTo(1)
+  check(subprojects.size == 1) { "Expected only a single subproject" }
   return buildDir(subprojects.first())
 }
 
@@ -37,17 +55,19 @@ public fun GradleProject.resolveFromSingleSubproject(relativePath: String): File
 }
 
 /**
- * Returns the path to the subproject of the given name in the build, asserting that there is only
- * one.
+ * Returns the path to the subproject of the given name in the build, asserting that there is only one. Uses "build" as
+ * the build directory name by default.
  */
-public fun GradleProject.buildPathForName(path: String): Path {
+public fun GradleProject.buildPathForName(path: String, buildDirName: String = "build"): Path {
   val project = if (path == ":") {
     rootProject
   } else {
-    subprojects.find { it.name == path }
+    subprojects
+      // normalize name/path string so users can pass in `:project` or `project` and it Just Works.
+      .single { it.name.ensurePrefix() == path.ensurePrefix() }
   }
-  assertWithMessage("No project with path $path").that(project as Any?).isNotNull()
-  return buildDir(project!!)
+
+  return buildDir(project = project, buildDirName = buildDirName)
 }
 
 /**
@@ -58,6 +78,10 @@ public fun GradleProject.buildFileForName(path: String): File = buildPathForName
 /**
  * Returns the file specified, relative to the subproject specified by [projectName].
  */
+@Deprecated(
+  "Use singleArtifact",
+  replaceWith = ReplaceWith("singleArtifact(projectName, relativePath)")
+)
 public fun GradleProject.resolveFromName(projectName: String, relativePath: String): File {
   return buildPathForName(projectName).resolve(relativePath).toFile()
 }
diff --git a/testkit/gradle-testkit-truth/build.gradle.kts b/testkit/gradle-testkit-truth/build.gradle.kts
index 2126b9802..7f479a4db 100644
--- a/testkit/gradle-testkit-truth/build.gradle.kts
+++ b/testkit/gradle-testkit-truth/build.gradle.kts
@@ -39,6 +39,9 @@ tasks.named("javadoc") {
 }
 
 dependencies {
+  api(project(":gradle-testkit-support")) {
+    because("Uses BuildArtifact")
+  }
   api(kotlin("stdlib"))
   api(gradleTestKit())
   api(libs.truth)
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/AbstractSubject.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/AbstractSubject.kt
new file mode 100644
index 000000000..8961ea493
--- /dev/null
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/AbstractSubject.kt
@@ -0,0 +1,28 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.truth
+
+import com.google.common.truth.Fact
+import com.google.common.truth.FailureMetadata
+import com.google.common.truth.Subject
+
+// We need to extend Subject because failWithActual() is protected in that class.
+public abstract class AbstractSubject<T> internal constructor(
+  failureMetadata: FailureMetadata,
+  actual: T?
+) : Subject(failureMetadata, actual) {
+
+  internal fun assertNonNull(actual: T?, message: () -> String): T {
+    if (actual == null) {
+      failWithActual(Fact.simpleFact(message.invoke()))
+    }
+    return actual!!
+  }
+
+  internal fun assertNonNull(actual: T?, key: String, value: Any?): T {
+    if (actual == null) {
+      failWithActual(key, value)
+    }
+    return actual!!
+  }
+}
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildResultSubject.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildResultSubject.kt
index 8cfda51f4..1153955ec 100644
--- a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildResultSubject.kt
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildResultSubject.kt
@@ -18,7 +18,7 @@ import org.gradle.testkit.runner.TaskOutcome
 public class BuildResultSubject private constructor(
   failureMetadata: FailureMetadata,
   private val actual: BuildResult?
-) : Subject(failureMetadata, actual) {
+) : AbstractSubject<BuildResult>(failureMetadata, actual) {
 
   public companion object {
     private val BUILD_RESULT_SUBJECT_FACTORY: Factory<BuildResultSubject, BuildResult> =
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildTaskSubject.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildTaskSubject.kt
index df2f94242..26f8c52ba 100644
--- a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildTaskSubject.kt
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/BuildTaskSubject.kt
@@ -4,7 +4,6 @@ package com.autonomousapps.kit.truth
 
 import com.google.common.collect.Iterables
 import com.google.common.truth.FailureMetadata
-import com.google.common.truth.Subject
 import com.google.common.truth.Subject.Factory
 import com.google.common.truth.Truth.assertAbout
 import com.google.errorprone.annotations.CanIgnoreReturnValue
@@ -14,7 +13,7 @@ import org.gradle.testkit.runner.TaskOutcome
 public class BuildTaskSubject private constructor(
   failureMetadata: FailureMetadata,
   private val actual: BuildTask?,
-) : Subject(failureMetadata, actual) {
+) : AbstractSubject<BuildTask>(failureMetadata, actual) {
 
   public companion object {
     private val BUILD_TASK_SUBJECT_FACTORY: Factory<BuildTaskSubject, BuildTask> =
@@ -49,10 +48,8 @@ public class BuildTaskSubject private constructor(
 
   @CanIgnoreReturnValue
   public fun hasOutcomeIn(outcomes: Iterable<TaskOutcome>): BuildTaskSubject {
-    if (actual == null) {
-      failWithActual("expected to have a value", outcomes)
-    }
-    if (!Iterables.contains(outcomes, actual!!.outcome)) {
+    val actual = assertNonNull(actual, "expected to have a value", outcomes)
+    if (!Iterables.contains(outcomes, actual.outcome)) {
       failWithActual("expected any of", outcomes)
     }
     return this
@@ -60,10 +57,8 @@ public class BuildTaskSubject private constructor(
 
   @CanIgnoreReturnValue
   public fun hasOutcomeIn(vararg outcomes: TaskOutcome): BuildTaskSubject {
-    if (actual == null) {
-      failWithActual("expected to have a value", outcomes)
-    }
-    if (!Iterables.contains(outcomes.toList(), actual!!.outcome)) {
+    val actual = assertNonNull(actual, "expected to have a value", outcomes)
+    if (!Iterables.contains(outcomes.toList(), actual.outcome)) {
       failWithActual("expected any of", outcomes.toList())
     }
     return this
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/TestKitTruth.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/TestKitTruth.kt
index a990ffafc..dc7f2b356 100644
--- a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/TestKitTruth.kt
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/TestKitTruth.kt
@@ -2,9 +2,12 @@
 // SPDX-License-Identifier: Apache-2.0
 package com.autonomousapps.kit.truth
 
+import com.autonomousapps.kit.artifacts.BuildArtifact
 import com.autonomousapps.kit.truth.BuildResultSubject.Companion.buildResults
 import com.autonomousapps.kit.truth.BuildTaskListSubject.Companion.buildTaskList
 import com.autonomousapps.kit.truth.BuildTaskSubject.Companion.buildTasks
+import com.autonomousapps.kit.truth.artifact.BuildArtifactsSubject
+import com.autonomousapps.kit.truth.artifact.BuildArtifactsSubject.Companion.buildArtifacts
 import com.google.common.truth.Truth.assertAbout
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.testkit.runner.BuildTask
@@ -12,18 +15,15 @@ import org.gradle.testkit.runner.BuildTask
 public class TestKitTruth {
   public companion object {
     @JvmStatic
-    public fun assertThat(target: BuildResult): BuildResultSubject {
-      return assertAbout(buildResults()).that(target)
-    }
+    public fun assertThat(target: BuildResult): BuildResultSubject = assertAbout(buildResults()).that(target)
 
     @JvmStatic
-    public fun assertThat(target: BuildTask): BuildTaskSubject {
-      return assertAbout(buildTasks()).that(target)
-    }
+    public fun assertThat(target: BuildTask): BuildTaskSubject = assertAbout(buildTasks()).that(target)
 
     @JvmStatic
-    public fun assertThat(target: List<BuildTask>): BuildTaskListSubject {
-      return assertAbout(buildTaskList()).that(target)
-    }
+    public fun assertThat(target: List<BuildTask>): BuildTaskListSubject = assertAbout(buildTaskList()).that(target)
+
+    @JvmStatic
+    public fun assertThat(target: BuildArtifact): BuildArtifactsSubject = assertAbout(buildArtifacts()).that(target)
   }
 }
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/BuildArtifactsSubject.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/BuildArtifactsSubject.kt
new file mode 100644
index 000000000..6eebc7cc1
--- /dev/null
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/BuildArtifactsSubject.kt
@@ -0,0 +1,112 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.truth.artifact
+
+import com.autonomousapps.kit.artifacts.BuildArtifact
+import com.autonomousapps.kit.artifacts.FileType
+import com.autonomousapps.kit.truth.AbstractSubject
+import com.google.common.truth.Fact
+import com.google.common.truth.FailureMetadata
+import com.google.common.truth.Subject.Factory
+import com.google.common.truth.Truth
+import com.google.errorprone.annotations.CanIgnoreReturnValue
+
+public class BuildArtifactsSubject private constructor(
+  failureMetadata: FailureMetadata,
+  private val actual: BuildArtifact?,
+) : AbstractSubject<BuildArtifact>(failureMetadata, actual) {
+
+  public companion object {
+    private val BUILD_ARTIFACT_SUBJECT_FACTORY: Factory<BuildArtifactsSubject, BuildArtifact> =
+      Factory { metadata, actual -> BuildArtifactsSubject(metadata, actual) }
+
+    @JvmStatic
+    public fun buildArtifacts(): Factory<BuildArtifactsSubject, BuildArtifact> = BUILD_ARTIFACT_SUBJECT_FACTORY
+
+    @JvmStatic
+    public fun assertThat(actual: BuildArtifact?): BuildArtifactsSubject {
+      return Truth.assertAbout(buildArtifacts()).that(actual)
+    }
+  }
+
+  @CanIgnoreReturnValue
+  public fun exists(): BuildArtifact {
+    val actual = assertNonNull(actual) { "build artifact was null" }
+    check(actual.exists())
+
+    return actual
+  }
+
+  @CanIgnoreReturnValue
+  public fun notExists(): BuildArtifact {
+    val actual = assertNonNull(actual) { "build artifact was null" }
+    check(actual.notExists())
+
+    return actual
+  }
+
+  @CanIgnoreReturnValue
+  public fun isRegularFile(): BuildArtifact {
+    val actual = assertNonNull(actual) { "build artifact was null" }
+    if (actual.notExists()) {
+      failWithActual(Fact.simpleFact("build artifact does not exist"))
+    }
+    check(actual.isRegularFile()) { "Expected regular file. Was ${FileType.from(actual).humanReadableName}" }
+
+    return actual
+  }
+
+  @CanIgnoreReturnValue
+  public fun isDirectory(): BuildArtifact {
+    val actual = assertNonNull(actual) { "build artifact was null" }
+    if (actual.notExists()) {
+      failWithActual(Fact.simpleFact("build artifact does not exist"))
+    }
+    check(actual.isDirectory()) { "Expected directory. Was ${FileType.from(actual).humanReadableName}" }
+
+    return actual
+  }
+
+  @CanIgnoreReturnValue
+  public fun isSymbolicLink(): BuildArtifact {
+    val actual = assertNonNull(actual) { "build artifact was null" }
+    if (actual.notExists()) {
+      failWithActual(Fact.simpleFact("build artifact does not exist"))
+    }
+    check(actual.isSymbolicLink()) { "Expected symbolic link. Was ${FileType.from(actual).humanReadableName}" }
+
+    return actual
+  }
+
+  @CanIgnoreReturnValue
+  public fun isJar(): BuildArtifact = isType("jar")
+
+  @CanIgnoreReturnValue
+  public fun isType(extension: String): BuildArtifact {
+    isRegularFile()
+
+    val actual = assertNonNull(actual) { "build artifact was null" }
+    if (actual.notExists()) {
+      failWithActual(Fact.simpleFact("build artifact does not exist"))
+    }
+
+    check(actual.extension == extension) { "Expected extension to be '$extension'. Was '${actual.extension}'" }
+
+    return actual
+  }
+
+  public fun jar(): JarSubject {
+    val actual = isJar()
+    return JarSubject.assertThat(actual.asPath)
+  }
+
+  public fun file(): PathSubject {
+    val actual = isRegularFile()
+
+    if (actual.notExists()) {
+      failWithActual(Fact.simpleFact("build artifact does not exist"))
+    }
+
+    return PathSubject.assertThat(actual.asPath)
+  }
+}
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/JarSubject.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/JarSubject.kt
new file mode 100644
index 000000000..dc6595ef3
--- /dev/null
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/JarSubject.kt
@@ -0,0 +1,52 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.truth.artifact
+
+import com.autonomousapps.kit.truth.AbstractSubject
+import com.google.common.truth.Fact
+import com.google.common.truth.FailureMetadata
+import com.google.common.truth.Subject.Factory
+import com.google.common.truth.Truth
+import java.nio.file.FileSystems
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.StandardCopyOption
+import kotlin.io.path.notExists
+
+public class JarSubject private constructor(
+  failureMetadata: FailureMetadata,
+  private val actual: Path?,
+) : AbstractSubject<Path>(failureMetadata, actual) {
+
+  public companion object {
+    private val JAR_SUBJECT_FACTORY: Factory<JarSubject, Path> =
+      Factory { metadata, actual -> JarSubject(metadata, actual) }
+
+    @JvmStatic
+    public fun jars(): Factory<JarSubject, Path> = JAR_SUBJECT_FACTORY
+
+    @JvmStatic
+    public fun assertThat(actual: Path?): JarSubject = Truth.assertAbout(jars()).that(actual)
+  }
+
+  public fun containsResource(path: String) {
+    resource(path).exists()
+  }
+
+  public fun resource(path: String): PathSubject {
+    val actual = assertNonNull(actual) { "jar was null" }
+
+    // Open zip, copy entry to temp dir, close zip.
+    val tempResource = FileSystems.newFileSystem(actual, null).use { fs ->
+      val resource = fs.getPath(path)
+      if (resource.notExists()) {
+        failWithActual(Fact.simpleFact("No resource found at '$path' in '$actual'"))
+      }
+
+      val tempDir = Files.createTempDirectory(null)
+      Files.copy(resource, tempDir.resolve(path), StandardCopyOption.REPLACE_EXISTING)
+    }
+
+    return PathSubject.assertThat(tempResource)
+  }
+}
diff --git a/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/PathSubject.kt b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/PathSubject.kt
new file mode 100644
index 000000000..25d288b35
--- /dev/null
+++ b/testkit/gradle-testkit-truth/src/main/kotlin/com/autonomousapps/kit/truth/artifact/PathSubject.kt
@@ -0,0 +1,65 @@
+// Copyright (c) 2024. Tony Robalik.
+// SPDX-License-Identifier: Apache-2.0
+package com.autonomousapps.kit.truth.artifact
+
+import com.autonomousapps.kit.truth.AbstractSubject
+import com.google.common.truth.*
+import com.google.common.truth.Subject.Factory
+import com.google.errorprone.annotations.CanIgnoreReturnValue
+import java.nio.charset.Charset
+import java.nio.file.Path
+import kotlin.io.path.exists
+import kotlin.io.path.notExists
+import kotlin.io.path.readLines
+import kotlin.io.path.readText
+
+public class PathSubject private constructor(
+  failureMetadata: FailureMetadata,
+  private val actual: Path?,
+) : AbstractSubject<Path>(failureMetadata, actual) {
+
+  public companion object {
+    private val PATH_SUBJECT_FACTORY: Factory<PathSubject, Path> =
+      Factory { metadata, actual -> PathSubject(metadata, actual) }
+
+    @JvmStatic
+    public fun paths(): Factory<PathSubject, Path> = PATH_SUBJECT_FACTORY
+
+    @JvmStatic
+    public fun assertThat(actual: Path?): PathSubject {
+      return Truth.assertAbout(paths()).that(actual)
+    }
+  }
+
+  @CanIgnoreReturnValue
+  public fun exists(): Path {
+    val actual = assertNonNull(actual) { "path was null" }
+    if (actual.notExists()) {
+      failWithActual(Fact.simpleFact("path does not exist"))
+    }
+
+    return actual
+  }
+
+  @CanIgnoreReturnValue
+  public fun notExists(): Path {
+    val actual = assertNonNull(actual) { "path was null" }
+    if (actual.exists()) {
+      failWithActual(Fact.simpleFact("path exists"))
+    }
+
+    return actual
+  }
+
+  @JvmOverloads
+  public fun text(charset: Charset = Charsets.UTF_8): StringSubject {
+    val actual = assertNonNull(actual) { "path was null" }
+    return check("readText()").that(actual.readText(charset))
+  }
+
+  @JvmOverloads
+  public fun lines(charset: Charset = Charsets.UTF_8): IterableSubject {
+    val actual = assertNonNull(actual) { "path was null" }
+    return check("readLines()").that(actual.readLines(charset))
+  }
+}
diff --git a/testkit/settings.gradle.kts b/testkit/settings.gradle.kts
index 27ac88435..c40e845ce 100644
--- a/testkit/settings.gradle.kts
+++ b/testkit/settings.gradle.kts
@@ -23,7 +23,7 @@ pluginManagement {
     }
   }
   plugins {
-    id("com.autonomousapps.testkit") version "0.4"
+    id("com.autonomousapps.testkit") version "0.8"
 
     id("com.github.johnrengelman.shadow") version "8.1.1"
     id("com.gradle.enterprise") version "3.15.1"