+
+ + +
+

Using the visualiserΒΆ

+

In order to assist with understanding of the state model, the repository includes a simple graph visualiser. The +visualiser is integrated with the unit test framework and the same domain specific language. It is currently very +early and the diagrams it produces are not especially beautiful. The intention is to improve it in future releases.

+_images/visualiser.png +

An example of how to use it can be seen in src/test/kotlin/contracts/CommercialPaperTests.kt.

+

Briefly, define a set of transactions in a group using the same DSL that is used in the unit tests. Here’s an example +of a trade lifecycle using the commercial paper contract

+
+
val group: TransactionGroupDSL<ContractState> = transactionGroupFor() {
+      roots {
+          transaction(900.DOLLARS.CASH `owned by` ALICE label "alice's $900")
+          transaction(someProfits.CASH `owned by` MEGA_CORP_PUBKEY label "some profits")
+      }
+
+      // Some CP is issued onto the ledger by MegaCorp.
+      transaction("Issuance") {
+          output("paper") { PAPER_1 }
+          arg(MEGA_CORP_PUBKEY) { CommercialPaper.Commands.Issue() }
+      }
+
+      // The CP is sold to alice for her $900, $100 less than the face value. At 10% interest after only 7 days,
+      // that sounds a bit too good to be true!
+      transaction("Trade") {
+          input("paper")
+          input("alice's $900")
+          output("borrowed $900") { 900.DOLLARS.CASH `owned by` MEGA_CORP_PUBKEY }
+          output("alice's paper") { "paper".output `owned by` ALICE }
+          arg(ALICE) { Cash.Commands.Move() }
+          arg(MEGA_CORP_PUBKEY) { CommercialPaper.Commands.Move() }
+      }
+
+      // Time passes, and Alice redeem's her CP for $1000, netting a $100 profit. MegaCorp has received $1200
+      // as a single payment from somewhere and uses it to pay Alice off, keeping the remaining $200 as change.
+      transaction("Redemption", redemptionTime) {
+          input("alice's paper")
+          input("some profits")
+
+          output("Alice's profit") { aliceGetsBack.CASH `owned by` ALICE }
+          output("Change") { (someProfits - aliceGetsBack).CASH `owned by` MEGA_CORP_PUBKEY }
+          if (!destroyPaperAtRedemption)
+              output { "paper".output }
+
+          arg(MEGA_CORP_PUBKEY) { Cash.Commands.Move() }
+          arg(ALICE) { CommercialPaper.Commands.Redeem() }
+      }
+  }
+
+
+
+

Now you can define a main method in your unit test class that takes the TransactionGroupDSL object and uses it:

+
+
CommercialPaperTests().trade().visualise()
+
+
+
+

This will open up a window with the following features:

+
    +
  • The nodes can be dragged around to try and obtain a better layout (an improved layout algorithm will be a future +feature).
    • +
  • States are rendered as circles. Transactions are small blue squares. Commands are small diamonds.
    • +
  • Clicking a state will open up a window that shows its fields.
    • +
+
+ + +
+