diff --git a/core/src/main/scala/com/eed3si9n/jarjarabrams/Main.scala b/core/src/main/scala/com/eed3si9n/jarjarabrams/Main.scala
index 33d0b40..2070bda 100644
--- a/core/src/main/scala/com/eed3si9n/jarjarabrams/Main.scala
+++ b/core/src/main/scala/com/eed3si9n/jarjarabrams/Main.scala
@@ -1,8 +1,7 @@
 package com.eed3si9n.jarjarabrams
 
-import com.eed3si9n.jarjar.{ MainUtil, RulesFileParser }
-import java.nio.file.Path;
-import scala.collection.JavaConverters._
+import com.eed3si9n.jarjar.MainUtil
+import java.nio.file.Path
 
 class Main {
   def help(): Unit = Main.printHelp()
@@ -11,11 +10,6 @@ class Main {
     if (rulesFile == null || inJar == null || outJar == null) {
       throw new IllegalArgumentException("rulesFile, inJar, and outJar are required");
     }
-    val rules = RulesFileParser
-      .parse(rulesFile.toFile)
-      .asScala
-      .toList
-      .map(Shader.toShadeRule)
     val verbose = java.lang.Boolean.getBoolean("verbose")
     val skipManifest = java.lang.Boolean.getBoolean("skipManifest")
     val resetTimestamp = sys.props.get("resetTimestamp") match {
@@ -23,7 +17,7 @@ class Main {
       case None    => true
     }
     Shader.shadeFile(
-      rules,
+      Shader.parseRulesFile(rulesFile),
       inJar,
       outJar,
       verbose,
diff --git a/core/src/main/scala/com/eed3si9n/jarjarabrams/Shader.scala b/core/src/main/scala/com/eed3si9n/jarjarabrams/Shader.scala
index bde85bd..981cd87 100644
--- a/core/src/main/scala/com/eed3si9n/jarjarabrams/Shader.scala
+++ b/core/src/main/scala/com/eed3si9n/jarjarabrams/Shader.scala
@@ -122,6 +122,9 @@ object Shader {
           None
     }
 
+  def parseRulesFile(rulesFile: Path): List[ShadeRule] =
+    RulesFileParser.parse(rulesFile.toFile()).asScala.map(toShadeRule).toList
+
   def toShadeRule(rule: PatternElement): ShadeRule =
     rule match {
       case r: Rule =>
diff --git a/core/src/main/scala/com/eed3si9n/jarjarabrams/Zip.scala b/core/src/main/scala/com/eed3si9n/jarjarabrams/Zip.scala
index 00ad467..782ba26 100644
--- a/core/src/main/scala/com/eed3si9n/jarjarabrams/Zip.scala
+++ b/core/src/main/scala/com/eed3si9n/jarjarabrams/Zip.scala
@@ -4,6 +4,7 @@ import com.eed3si9n.jarjar.util.EntryStruct
 import java.nio.file.{ Files, NoSuchFileException, Path }
 import java.nio.file.attribute.FileTime
 import java.io.{ ByteArrayOutputStream, FileNotFoundException, InputStream, OutputStream }
+import java.security.MessageDigest
 import java.util.jar.JarEntry
 import scala.annotation.tailrec
 import scala.collection.JavaConverters._
@@ -51,7 +52,7 @@ object Zip {
       val tempJar = Files.createTempFile("jarjar", ".jar")
       Using.jarOutputStream(tempJar) { out =>
         val names = new mutable.HashSet[String]
-        in.entries.asScala.toList.foreach { entry0 =>
+        in.entries.asScala.foreach { entry0 =>
           val struct0 = entryStruct(
             entry0.getName,
             entry0.getTime,
@@ -189,4 +190,23 @@ object Zip {
   def createDirectories(p: Path): Unit =
     if (Files.exists(p)) ()
     else Files.createDirectories(p)
+
+  def sha256(p: Path): String =
+    Using.fileInputStream(p) { in =>
+      val digest = MessageDigest.getInstance("SHA-256")
+      val hash = digest.digest(toByteArray(in))
+      toHex(hash)
+    }
+
+  private def toHex(bytes: Array[Byte]): String = {
+    val buffer = new StringBuilder(bytes.length * 2)
+    for { i <- bytes.indices } {
+      val hex = Integer.toHexString(bytes(i) & 0xff)
+      if (hex.length() == 1) {
+        buffer.append('0')
+      }
+      buffer.append(hex)
+    }
+    buffer.toString
+  }
 }
diff --git a/core/src/test/scala/testpkg/ShaderTest.scala b/core/src/test/scala/testpkg/ShaderTest.scala
index badb7bf..0519340 100644
--- a/core/src/test/scala/testpkg/ShaderTest.scala
+++ b/core/src/test/scala/testpkg/ShaderTest.scala
@@ -2,23 +2,70 @@ package testpkg
 
 import verify._
 import java.nio.file.{ Files, Path, Paths }
-import com.eed3si9n.jarjarabrams.{ Main, Zip }
+import com.eed3si9n.jarjarabrams.{ Shader, Zip }
 
 object ShaderTest extends BasicTestSuite {
+  final val byteBuddyJar = "example/byte-buddy-agent.jar"
+  final val shapelessJar = "example/shapeless_2.12-2.3.2.jar"
+  final val expectedByteBuddyClass = "foo/Attacher.class"
+  final val expectedShapelessClass = "bar/shapeless/Poly8.class"
+
   test("shade bytebuddy") {
-    testShading(Paths.get("example/byte-buddy-agent.jar"), "foo/Attacher.class")
+    testShading(
+      Paths.get(byteBuddyJar),
+      resetTimestamp = false,
+      expectedClass = expectedByteBuddyClass,
+      expectedSha = "6e7372e52e3b2e981ffa42fc29d5cec1cc84431972d45fb51d605210e11c3ebd"
+    )
+  }
+
+  test("shade bytebuddy (resetTimestamp)") {
+    testShading(
+      Paths.get(byteBuddyJar),
+      resetTimestamp = true,
+      expectedClass = expectedByteBuddyClass,
+      expectedSha = "33ceee11fb2b5e4d46ebe552025bc17bc4d9391974c55e07d63f9e85d2ec381a"
+    )
   }
 
   test("shade shapeless") {
-    testShading(Paths.get("example/shapeless_2.12-2.3.2.jar"), "bar/shapeless/Poly8.class")
+    testShading(
+      Paths.get(shapelessJar),
+      resetTimestamp = false,
+      expectedClass = expectedShapelessClass,
+      expectedSha = "b0675ab6b2171faad08de45ccbc4674df569e03b434745ebd9e7442cd7846796"
+    )
+  }
+
+  test("shade shapeless (resetTimestamp)") {
+    testShading(
+      Paths.get(shapelessJar),
+      resetTimestamp = true,
+      expectedClass = expectedShapelessClass,
+      expectedSha = "68ac892591bb30eb2ba5c0c2c3195e7529e15bacd221b8bb3d75b154f5a4ce76"
+    )
   }
 
-  def testShading(inJar: Path, expectedClass: String): Unit = {
+  def testShading(
+      inJar: Path,
+      resetTimestamp: Boolean,
+      expectedClass: String,
+      expectedSha: String
+  ): Unit = {
     val tempJar = Files.createTempFile("test", ".jar")
     Files.delete(tempJar)
-    val rules = Paths.get("example/shade.rules")
-    new Main().process(rules, inJar, tempJar)
+    val rules = Shader.parseRulesFile(Paths.get("example/shade.rules"))
+    Shader.shadeFile(
+      rules,
+      inJar,
+      tempJar,
+      verbose = false,
+      skipManifest = false,
+      resetTimestamp
+    )
     val entries = Zip.list(tempJar).map(_._1)
     assert(entries.contains(expectedClass))
+    val actualSha = Zip.sha256(tempJar)
+    assert(actualSha == expectedSha)
   }
 }