diff --git a/contracts/src/test/java/com/r3corda/contracts/asset/CashTestsJava.java b/contracts/src/test/java/com/r3corda/contracts/asset/CashTestsJava.java
index 36fced1951..e3fdbd9acf 100644
--- a/contracts/src/test/java/com/r3corda/contracts/asset/CashTestsJava.java
+++ b/contracts/src/test/java/com/r3corda/contracts/asset/CashTestsJava.java
@@ -14,7 +14,7 @@ import static com.r3corda.contracts.testing.JavaTestHelpers.*;
  */
 public class CashTestsJava {
 
-    private OpaqueBytes defaultRef = new OpaqueBytes(new byte[]{1});;
+    private OpaqueBytes defaultRef = new OpaqueBytes(new byte[]{1});
     private PartyAndReference defaultIssuer = getMEGA_CORP().ref(defaultRef);
     private Cash.State inState = new Cash.State(issuedBy(DOLLARS(1000), defaultIssuer), getDUMMY_PUBKEY_1());
     private Cash.State outState = new Cash.State(inState.getAmount(), getDUMMY_PUBKEY_2());
diff --git a/contracts/src/test/kotlin/com/r3corda/contracts/CommercialPaperTests.kt b/contracts/src/test/kotlin/com/r3corda/contracts/CommercialPaperTests.kt
index 992b76d1a6..7c436e6db2 100644
--- a/contracts/src/test/kotlin/com/r3corda/contracts/CommercialPaperTests.kt
+++ b/contracts/src/test/kotlin/com/r3corda/contracts/CommercialPaperTests.kt
@@ -97,7 +97,7 @@ class CommercialPaperTestsGeneric {
                 input("alice's paper")
                 input("some profits")
 
-                fun TransactionDSL<EnforceVerifyOrFail, TransactionDSLInterpreter<EnforceVerifyOrFail>>.outputs(aliceGetsBack: Amount<Issued<Currency>>) {
+                fun TransactionDSL<TransactionDSLInterpreter>.outputs(aliceGetsBack: Amount<Issued<Currency>>) {
                     output("Alice's profit") { aliceGetsBack.STATE `owned by` ALICE_PUBKEY }
                     output("Change") { (someProfits - aliceGetsBack).STATE `owned by` MEGA_CORP_PUBKEY }
                 }
diff --git a/contracts/src/test/kotlin/com/r3corda/contracts/IRSTests.kt b/contracts/src/test/kotlin/com/r3corda/contracts/IRSTests.kt
index ad5e16482f..643d4f7581 100644
--- a/contracts/src/test/kotlin/com/r3corda/contracts/IRSTests.kt
+++ b/contracts/src/test/kotlin/com/r3corda/contracts/IRSTests.kt
@@ -360,7 +360,7 @@ class IRSTests {
     /**
      * Generates a typical transactional history for an IRS.
      */
-    fun trade(): LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter> {
+    fun trade(): LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter> {
 
         val ld = LocalDate.of(2016, 3, 8)
         val bd = BigDecimal("0.0063518")
@@ -653,7 +653,7 @@ class IRSTests {
      * result and the grouping won't work either.
      * In reality, the only fields that should be in common will be the next fixing date and the reference rate.
      */
-    fun tradegroups(): LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter> {
+    fun tradegroups(): LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter> {
         val ld1 = LocalDate.of(2016, 3, 8)
         val bd1 = BigDecimal("0.0063518")
 
diff --git a/contracts/src/test/kotlin/com/r3corda/contracts/asset/ObligationTests.kt b/contracts/src/test/kotlin/com/r3corda/contracts/asset/ObligationTests.kt
index 023f28c34b..a37c250c6d 100644
--- a/contracts/src/test/kotlin/com/r3corda/contracts/asset/ObligationTests.kt
+++ b/contracts/src/test/kotlin/com/r3corda/contracts/asset/ObligationTests.kt
@@ -5,7 +5,6 @@ import com.r3corda.contracts.testing.*
 import com.r3corda.core.contracts.*
 import com.r3corda.core.crypto.SecureHash
 import com.r3corda.core.testing.*
-import com.r3corda.core.testing.JavaTestHelpers
 import com.r3corda.core.utilities.nonEmptySetOf
 import org.junit.Test
 import java.security.PublicKey
@@ -35,7 +34,7 @@ class ObligationTests {
     val outState = inState.copy(beneficiary = DUMMY_PUBKEY_2)
 
     private fun obligationTestRoots(
-            group: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>
+            group: LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>
     ) = group.apply {
         unverifiedTransaction {
             output("Alice's $1,000,000 obligation to Bob", oneMillionDollars.OBLIGATION between Pair(ALICE, BOB_PUBKEY))
diff --git a/core/src/main/kotlin/com/r3corda/core/testing/LedgerDSLInterpreter.kt b/core/src/main/kotlin/com/r3corda/core/testing/LedgerDSLInterpreter.kt
index c80aa84a9d..8b6329956e 100644
--- a/core/src/main/kotlin/com/r3corda/core/testing/LedgerDSLInterpreter.kt
+++ b/core/src/main/kotlin/com/r3corda/core/testing/LedgerDSLInterpreter.kt
@@ -18,12 +18,64 @@ interface OutputStateLookup {
     fun <S : ContractState> retrieveOutputStateAndRef(clazz: Class<S>, label: String): StateAndRef<S>
 }
 
+/**
+ * This interface asserts that the DSL at hand is capable of verifying it's underlying construct(ledger/transaction)
+ */
+interface Verifies {
+    /**
+     * Verifies the ledger/transaction, throws if the verification fails.
+     */
+    fun verifies(): EnforceVerifyOrFail
+
+    /**
+     * Asserts that verifies() throws
+     * @param expectedMessage: An optional string to be searched for in the raised exception.
+     */
+    fun failsWith(expectedMessage: String?): EnforceVerifyOrFail {
+        val exceptionThrown = try {
+            verifies()
+            false
+        } catch (exception: Exception) {
+            if (expectedMessage != null) {
+                val exceptionMessage = exception.message
+                if (exceptionMessage == null) {
+                    throw AssertionError(
+                            "Expected exception containing '$expectedMessage' but raised exception had no message"
+                    )
+                } else if (!exceptionMessage.toLowerCase().contains(expectedMessage.toLowerCase())) {
+                    throw AssertionError(
+                            "Expected exception containing '$expectedMessage' but raised exception was '$exception'"
+                    )
+                }
+            }
+            true
+        }
+
+        if (!exceptionThrown) {
+            throw AssertionError("Expected exception but didn't get one")
+        }
+
+        return EnforceVerifyOrFail.Token
+    }
+
+    /**
+     * Asserts that [verifies] throws, with no condition on the exception message
+     */
+    fun fails() = failsWith(null)
+
+    /**
+     * @see failsWith
+     */
+    infix fun `fails with`(msg: String) = failsWith(msg)
+}
+
+
 /**
  * This interface defines the bare bone functionality that a Ledger DSL interpreter should implement.
  *
  * TODO (Kotlin 1.1): Use type synonyms to make the type params less unwieldy
  */
-interface LedgerDSLInterpreter<R, out T : TransactionDSLInterpreter<R>> : OutputStateLookup {
+interface LedgerDSLInterpreter<out T : TransactionDSLInterpreter> : Verifies, OutputStateLookup {
     /**
      * Creates and adds a transaction to the ledger.
      * @param transactionLabel: Optional label of the transaction, to be used in diagnostic messages.
@@ -32,7 +84,7 @@ interface LedgerDSLInterpreter<R, out T : TransactionDSLInterpreter<R>> : Output
      * @return: The final [WireTransaction] of the built transaction.
      */
     fun _transaction(transactionLabel: String?, transactionBuilder: TransactionBuilder,
-                     dsl: TransactionDSL<R, T>.() -> R): WireTransaction
+                     dsl: TransactionDSL<T>.() -> EnforceVerifyOrFail): WireTransaction
 
     /**
      * Creates and adds a transaction to the ledger that will not be verified by [verifies].
@@ -42,13 +94,13 @@ interface LedgerDSLInterpreter<R, out T : TransactionDSLInterpreter<R>> : Output
      * @return: The final [WireTransaction] of the built transaction.
      */
     fun _unverifiedTransaction(transactionLabel: String?, transactionBuilder: TransactionBuilder,
-                               dsl: TransactionDSL<R, T>.() -> Unit): WireTransaction
+                               dsl: TransactionDSL<T>.() -> Unit): WireTransaction
 
     /**
      * Creates a local scoped copy of the ledger.
      * @param dsl: The ledger DSL to be interpreted using the copy.
      */
-    fun tweak(dsl: LedgerDSL<R, T, LedgerDSLInterpreter<R, T>>.() -> Unit)
+    fun tweak(dsl: LedgerDSL<T, LedgerDSLInterpreter<T>>.() -> Unit)
 
     /**
      * Adds an attachment to the ledger.
@@ -57,16 +109,6 @@ interface LedgerDSLInterpreter<R, out T : TransactionDSLInterpreter<R>> : Output
      */
     fun attachment(attachment: InputStream): SecureHash
 
-    /**
-     * Verifies the ledger using [TransactionGroup.verify], throws if the verification fails.
-     */
-    fun verifies()
-
-    /**
-     * Verifies the ledger, expecting an exception to be thrown.
-     * @param expectedMessage: An optional string to be searched for in the raised exception.
-     */
-    fun failsWith(expectedMessage: String?)
 }
 
 /**
@@ -75,22 +117,22 @@ interface LedgerDSLInterpreter<R, out T : TransactionDSLInterpreter<R>> : Output
  * functionality then first add your primitive to [LedgerDSLInterpreter] and then add the convenience defaults/extension
  * methods here.
  */
-class LedgerDSL<R, out T : TransactionDSLInterpreter<R>, out L : LedgerDSLInterpreter<R, T>> (val interpreter: L) :
-        LedgerDSLInterpreter<R, TransactionDSLInterpreter<R>> by interpreter {
+class LedgerDSL<out T : TransactionDSLInterpreter, out L : LedgerDSLInterpreter<T>> (val interpreter: L) :
+        LedgerDSLInterpreter<TransactionDSLInterpreter> by interpreter {
 
     /**
      * @see LedgerDSLInterpreter._transaction
      */
     @JvmOverloads
     fun transaction(label: String? = null, transactionBuilder: TransactionBuilder = TransactionBuilder(),
-                    dsl: TransactionDSL<R, TransactionDSLInterpreter<R>>.() -> R) =
+                    dsl: TransactionDSL<TransactionDSLInterpreter>.() -> EnforceVerifyOrFail) =
             _transaction(label, transactionBuilder, dsl)
     /**
      * @see LedgerDSLInterpreter._unverifiedTransaction
      */
     @JvmOverloads
     fun unverifiedTransaction(label: String? = null, transactionBuilder: TransactionBuilder = TransactionBuilder(),
-                    dsl: TransactionDSL<R, TransactionDSLInterpreter<R>>.() -> Unit) =
+                    dsl: TransactionDSL<TransactionDSLInterpreter>.() -> Unit) =
             _unverifiedTransaction(label, transactionBuilder, dsl)
 
     /**
@@ -117,14 +159,4 @@ class LedgerDSL<R, out T : TransactionDSLInterpreter<R>, out L : LedgerDSLInterp
      */
     fun <S : ContractState> retrieveOutput(clazz: Class<S>, label: String) =
             retrieveOutputStateAndRef(clazz, label).state.data
-
-    /**
-     * Asserts that the transaction will fail verification
-     */
-    fun fails() = failsWith(null)
-
-    /**
-     * @see TransactionDSLInterpreter.failsWith
-     */
-    infix fun `fails with`(msg: String) = failsWith(msg)
 }
diff --git a/core/src/main/kotlin/com/r3corda/core/testing/TestDSL.kt b/core/src/main/kotlin/com/r3corda/core/testing/TestDSL.kt
index 8a820c18a0..d950506da2 100644
--- a/core/src/main/kotlin/com/r3corda/core/testing/TestDSL.kt
+++ b/core/src/main/kotlin/com/r3corda/core/testing/TestDSL.kt
@@ -47,10 +47,7 @@ import java.util.*
 fun transaction(
         transactionLabel: String? = null,
         transactionBuilder: TransactionBuilder = TransactionBuilder(),
-        dsl: TransactionDSL<
-                EnforceVerifyOrFail,
-                TransactionDSLInterpreter<EnforceVerifyOrFail>
-        >.() -> EnforceVerifyOrFail
+        dsl: TransactionDSL<TransactionDSLInterpreter>.() -> EnforceVerifyOrFail
 ) = JavaTestHelpers.transaction(transactionLabel, transactionBuilder, dsl)
 
 /**
@@ -59,7 +56,7 @@ fun transaction(
 fun ledger(
         identityService: IdentityService = MOCK_IDENTITY_SERVICE,
         storageService: StorageService = MockStorageService(),
-        dsl: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit
+        dsl: LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit
 ) = JavaTestHelpers.ledger(identityService, storageService, dsl)
 
 @Deprecated(
@@ -67,8 +64,8 @@ fun ledger(
         replaceWith = ReplaceWith("tweak"),
         level = DeprecationLevel.ERROR)
 @Suppress("UNUSED_PARAMETER")
-fun TransactionDSLInterpreter<EnforceVerifyOrFail>.ledger(
-        dsl: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit) {
+fun TransactionDSLInterpreter.ledger(
+        dsl: LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit) {
 }
 
 @Deprecated(
@@ -76,11 +73,8 @@ fun TransactionDSLInterpreter<EnforceVerifyOrFail>.ledger(
         replaceWith = ReplaceWith("tweak"),
         level = DeprecationLevel.ERROR)
 @Suppress("UNUSED_PARAMETER")
-fun TransactionDSLInterpreter<EnforceVerifyOrFail>.transaction(
-        dsl: TransactionDSL<
-                EnforceVerifyOrFail,
-                TransactionDSLInterpreter<EnforceVerifyOrFail>
-                >.() -> EnforceVerifyOrFail) {
+fun TransactionDSLInterpreter.transaction(
+        dsl: TransactionDSL<TransactionDSLInterpreter>.() -> EnforceVerifyOrFail) {
 }
 
 @Deprecated(
@@ -88,8 +82,8 @@ fun TransactionDSLInterpreter<EnforceVerifyOrFail>.transaction(
         replaceWith = ReplaceWith("tweak"),
         level = DeprecationLevel.ERROR)
 @Suppress("UNUSED_PARAMETER")
-fun LedgerDSLInterpreter<EnforceVerifyOrFail, TransactionDSLInterpreter<EnforceVerifyOrFail>>.ledger(
-        dsl: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit) {
+fun LedgerDSLInterpreter<TransactionDSLInterpreter>.ledger(
+        dsl: LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit) {
 }
 
 /**
@@ -113,7 +107,7 @@ data class TestTransactionDSLInterpreter private constructor(
         override val ledgerInterpreter: TestLedgerDSLInterpreter,
         val transactionBuilder: TransactionBuilder,
         internal val labelToIndexMap: HashMap<String, Int>
-) : TransactionDSLInterpreter<EnforceVerifyOrFail>, OutputStateLookup by ledgerInterpreter {
+) : TransactionDSLInterpreter, OutputStateLookup by ledgerInterpreter {
 
     constructor(
             ledgerInterpreter: TestLedgerDSLInterpreter,
@@ -160,19 +154,8 @@ data class TestTransactionDSLInterpreter private constructor(
         return EnforceVerifyOrFail.Token
     }
 
-    override fun failsWith(expectedMessage: String?): EnforceVerifyOrFail {
-        expectExceptionContainingString(expectedMessage) {
-            this.verifies()
-        }
-
-        return EnforceVerifyOrFail.Token
-    }
-
     override fun tweak(
-            dsl: TransactionDSL<
-                    EnforceVerifyOrFail,
-                    TransactionDSLInterpreter<EnforceVerifyOrFail>
-                    >.() -> EnforceVerifyOrFail
+            dsl: TransactionDSL<TransactionDSLInterpreter>.() -> EnforceVerifyOrFail
     ) = dsl(TransactionDSL(copy()))
 }
 
@@ -182,7 +165,7 @@ data class TestLedgerDSLInterpreter private constructor (
         internal val labelToOutputStateAndRefs: HashMap<String, StateAndRef<ContractState>> = HashMap(),
         private val transactionWithLocations: HashMap<SecureHash, WireTransactionWithLocation> = HashMap(),
         private val nonVerifiedTransactionWithLocations: HashMap<SecureHash, WireTransactionWithLocation> = HashMap()
-) : LedgerDSLInterpreter<EnforceVerifyOrFail, TestTransactionDSLInterpreter> {
+) : LedgerDSLInterpreter<TestTransactionDSLInterpreter> {
     val wireTransactions: List<WireTransaction> get() = transactionWithLocations.values.map { it.transaction }
 
     // We specify [labelToOutputStateAndRefs] just so that Kotlin picks the primary constructor instead of cycling
@@ -260,7 +243,7 @@ data class TestLedgerDSLInterpreter private constructor (
 
     private fun <R> interpretTransactionDsl(
             transactionBuilder: TransactionBuilder,
-            dsl: TransactionDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter>.() -> R
+            dsl: TransactionDSL<TestTransactionDSLInterpreter>.() -> R
     ): TestTransactionDSLInterpreter {
         val transactionInterpreter = TestTransactionDSLInterpreter(this, transactionBuilder)
         dsl(TransactionDSL(transactionInterpreter))
@@ -292,7 +275,7 @@ data class TestLedgerDSLInterpreter private constructor (
     private fun <R> recordTransactionWithTransactionMap(
             transactionLabel: String?,
             transactionBuilder: TransactionBuilder,
-            dsl: TransactionDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter>.() -> R,
+            dsl: TransactionDSL<TestTransactionDSLInterpreter>.() -> R,
             transactionMap: HashMap<SecureHash, WireTransactionWithLocation> = HashMap()
     ): WireTransaction {
         val transactionLocation = getCallerLocation()
@@ -316,25 +299,25 @@ data class TestLedgerDSLInterpreter private constructor (
     override fun _transaction(
             transactionLabel: String?,
             transactionBuilder: TransactionBuilder,
-            dsl: TransactionDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter>.() -> EnforceVerifyOrFail
+            dsl: TransactionDSL<TestTransactionDSLInterpreter>.() -> EnforceVerifyOrFail
     ) = recordTransactionWithTransactionMap(transactionLabel, transactionBuilder, dsl, transactionWithLocations)
 
     override fun _unverifiedTransaction(
             transactionLabel: String?,
             transactionBuilder: TransactionBuilder,
-            dsl: TransactionDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter>.() -> Unit
+            dsl: TransactionDSL<TestTransactionDSLInterpreter>.() -> Unit
     ) = recordTransactionWithTransactionMap(transactionLabel, transactionBuilder, dsl, nonVerifiedTransactionWithLocations)
 
     override fun tweak(
-            dsl: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter,
-                    LedgerDSLInterpreter<EnforceVerifyOrFail, TestTransactionDSLInterpreter>>.() -> Unit) =
+            dsl: LedgerDSL<TestTransactionDSLInterpreter,
+                    LedgerDSLInterpreter<TestTransactionDSLInterpreter>>.() -> Unit) =
             dsl(LedgerDSL(copy()))
 
     override fun attachment(attachment: InputStream): SecureHash {
         return storageService.attachments.importAttachment(attachment)
     }
 
-    override fun verifies() {
+    override fun verifies(): EnforceVerifyOrFail {
         val transactionGroup = toTransactionGroup()
         try {
             transactionGroup.verify()
@@ -343,12 +326,8 @@ data class TestLedgerDSLInterpreter private constructor (
             val transactionName = transactionWithLocation?.label ?: transactionWithLocation?.location ?: "<unknown>"
             throw VerifiesFailed(transactionName, exception)
         }
-    }
 
-    override fun failsWith(expectedMessage: String?) {
-        expectExceptionContainingString(expectedMessage) {
-            this.verifies()
-        }
+        return EnforceVerifyOrFail.Token
     }
 
     override fun <S : ContractState> retrieveOutputStateAndRef(clazz: Class<S>, label: String): StateAndRef<S> {
@@ -389,30 +368,5 @@ fun signAll(transactionsToSign: List<WireTransaction>, extraKeys: Array<out KeyP
  * @param extraKeys: extra keys to sign transactions with.
  * @return: List of [SignedTransaction]s.
  */
-fun LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.signAll(
+fun LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.signAll(
         vararg extraKeys: KeyPair) = signAll(this.interpreter.wireTransactions, extraKeys)
-
-internal inline fun expectExceptionContainingString(string: String?, body:() -> Unit) {
-    val exceptionThrown = try {
-        body()
-        false
-    } catch (exception: Exception) {
-        if (string != null) {
-            val exceptionMessage = exception.message
-            if (exceptionMessage == null) {
-                throw AssertionError(
-                        "Expected exception containing '$string' but raised exception had no message"
-                )
-            } else if (!exceptionMessage.toLowerCase().contains(string.toLowerCase())) {
-                throw AssertionError(
-                        "Expected exception containing '$string' but raised exception was '$exception'"
-                )
-            }
-        }
-        true
-    }
-
-    if (!exceptionThrown) {
-        throw AssertionError("Expected exception but didn't get one")
-    }
-}
diff --git a/core/src/main/kotlin/com/r3corda/core/testing/TestUtils.kt b/core/src/main/kotlin/com/r3corda/core/testing/TestUtils.kt
index b649b0e63e..88e3de34f7 100644
--- a/core/src/main/kotlin/com/r3corda/core/testing/TestUtils.kt
+++ b/core/src/main/kotlin/com/r3corda/core/testing/TestUtils.kt
@@ -97,8 +97,8 @@ object JavaTestHelpers {
     @JvmStatic @JvmOverloads fun ledger(
             identityService: IdentityService = MOCK_IDENTITY_SERVICE,
             storageService: StorageService = MockStorageService(),
-            dsl: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit
-    ): LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter> {
+            dsl: LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.() -> Unit
+    ): LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter> {
         val ledgerDsl = LedgerDSL(TestLedgerDSLInterpreter(identityService, storageService))
         dsl(ledgerDsl)
         return ledgerDsl
@@ -111,10 +111,7 @@ object JavaTestHelpers {
     @JvmStatic @JvmOverloads fun transaction(
             transactionLabel: String? = null,
             transactionBuilder: TransactionBuilder = TransactionBuilder(),
-            dsl: TransactionDSL<
-                    EnforceVerifyOrFail,
-                    TransactionDSLInterpreter<EnforceVerifyOrFail>
-                    >.() -> EnforceVerifyOrFail
+            dsl: TransactionDSL<TransactionDSLInterpreter>.() -> EnforceVerifyOrFail
     ) = ledger { this.transaction(transactionLabel, transactionBuilder, dsl) }
 }
 
diff --git a/core/src/main/kotlin/com/r3corda/core/testing/TransactionDSLInterpreter.kt b/core/src/main/kotlin/com/r3corda/core/testing/TransactionDSLInterpreter.kt
index 2816d77990..0edb41f944 100644
--- a/core/src/main/kotlin/com/r3corda/core/testing/TransactionDSLInterpreter.kt
+++ b/core/src/main/kotlin/com/r3corda/core/testing/TransactionDSLInterpreter.kt
@@ -13,11 +13,11 @@ import java.time.Instant
  * @param <R>: The return type of [verifies]/[failsWith] and the like. It is generic so that we have control over whether
  * we want to enforce users to call these methods (@see [EnforceVerifyOrFail]) or not.
  */
-interface TransactionDSLInterpreter<R> : OutputStateLookup {
+interface TransactionDSLInterpreter : Verifies, OutputStateLookup {
     /**
      * A reference to the enclosing ledger{..}'s interpreter.
      */
-    val ledgerInterpreter: LedgerDSLInterpreter<R, TransactionDSLInterpreter<R>>
+    val ledgerInterpreter: LedgerDSLInterpreter<TransactionDSLInterpreter>
 
     /**
      * Adds an input reference to the transaction. Note that [verifies] will resolve this reference.
@@ -46,31 +46,19 @@ interface TransactionDSLInterpreter<R> : OutputStateLookup {
      */
     fun _command(signers: List<PublicKey>, commandData: CommandData)
 
-    /**
-     * Verifies the transaction.
-     * @return: Possibly a token confirming that [verifies] has been called.
-     */
-    fun verifies(): R
-
-    /**
-     * Verifies the transaction, expecting an exception to be thrown.
-     * @param expectedMessage: An optional string to be searched for in the raised exception.
-     */
-    fun failsWith(expectedMessage: String?): R
-
     /**
      * Creates a local scoped copy of the transaction.
      * @param dsl: The transaction DSL to be interpreted using the copy.
      */
-    fun tweak(dsl: TransactionDSL<R, TransactionDSLInterpreter<R>>.() -> R): R
+    fun tweak(dsl: TransactionDSL<TransactionDSLInterpreter>.() -> EnforceVerifyOrFail): EnforceVerifyOrFail
 }
 
-class TransactionDSL<R, out T : TransactionDSLInterpreter<R>> (val interpreter: T) :
-        TransactionDSLInterpreter<R> by interpreter {
+class TransactionDSL<out T : TransactionDSLInterpreter> (val interpreter: T) :
+        TransactionDSLInterpreter by interpreter {
 
     /**
      * Looks up the output label and adds the found state as an input.
-     * @param stateLabel: The label of the output state specified when calling [LedgerDSLInterpreter._output] and friends.
+     * @param stateLabel: The label of the output state specified when calling [TransactionDSLInterpreter._output] and friends.
      */
     fun input(stateLabel: String) = input(retrieveOutputStateAndRef(ContractState::class.java, stateLabel).ref)
 
@@ -128,14 +116,4 @@ class TransactionDSL<R, out T : TransactionDSLInterpreter<R>> (val interpreter:
      */
     @JvmOverloads
     fun timestamp(data: TimestampCommand, notary: PublicKey = DUMMY_NOTARY.owningKey) = command(notary, data)
-
-    /**
-     * Asserts that the transaction will fail verification
-     */
-    fun fails() = failsWith(null)
-
-    /**
-     * @see TransactionDSLInterpreter.failsWith
-     */
-    infix fun `fails with`(msg: String) = failsWith(msg)
 }
diff --git a/node/src/test/kotlin/com/r3corda/node/messaging/TwoPartyTradeProtocolTests.kt b/node/src/test/kotlin/com/r3corda/node/messaging/TwoPartyTradeProtocolTests.kt
index 2e25ab1abf..62863f46dc 100644
--- a/node/src/test/kotlin/com/r3corda/node/messaging/TwoPartyTradeProtocolTests.kt
+++ b/node/src/test/kotlin/com/r3corda/node/messaging/TwoPartyTradeProtocolTests.kt
@@ -17,7 +17,6 @@ import com.r3corda.core.node.services.ServiceType
 import com.r3corda.core.node.services.TransactionStorage
 import com.r3corda.core.node.services.Wallet
 import com.r3corda.core.random63BitValue
-import com.r3corda.core.seconds
 import com.r3corda.core.testing.*
 import com.r3corda.core.utilities.BriefLogFormatter
 import com.r3corda.node.internal.testing.MockNetwork
@@ -366,7 +365,7 @@ class TwoPartyTradeProtocolTests {
         }
     }
 
-    private fun LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.runWithError(
+    private fun LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.runWithError(
             bobError: Boolean,
             aliceError: Boolean,
             expectedMessageSubstring: String
@@ -431,7 +430,7 @@ class TwoPartyTradeProtocolTests {
         return signed.associateBy { it.id }
     }
 
-    private fun LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.fillUpForBuyer(
+    private fun LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.fillUpForBuyer(
             withError: Boolean,
             owner: PublicKey = BOB_PUBKEY,
             issuer: PartyAndReference = MEGA_CORP.ref(1)): Pair<Wallet, List<WireTransaction>> {
@@ -472,7 +471,7 @@ class TwoPartyTradeProtocolTests {
         return Pair(wallet, listOf(eb1, bc1, bc2))
     }
 
-    private fun LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.fillUpForSeller(
+    private fun LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>.fillUpForSeller(
             withError: Boolean,
             owner: PublicKey,
             amount: Amount<Issued<Currency>>,
diff --git a/node/src/test/kotlin/com/r3corda/node/visualiser/GroupToGraphConversion.kt b/node/src/test/kotlin/com/r3corda/node/visualiser/GroupToGraphConversion.kt
index 6b61416d5a..e57cffe02d 100644
--- a/node/src/test/kotlin/com/r3corda/node/visualiser/GroupToGraphConversion.kt
+++ b/node/src/test/kotlin/com/r3corda/node/visualiser/GroupToGraphConversion.kt
@@ -9,7 +9,7 @@ import org.graphstream.graph.Node
 import org.graphstream.graph.implementations.SingleGraph
 import kotlin.reflect.memberProperties
 
-class GraphVisualiser(val dsl: LedgerDSL<EnforceVerifyOrFail, TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>) {
+class GraphVisualiser(val dsl: LedgerDSL<TestTransactionDSLInterpreter, TestLedgerDSLInterpreter>) {
     companion object {
         val css = GraphVisualiser::class.java.getResourceAsStream("graph.css").bufferedReader().readText()
     }