feat(journal): core:journal module — decision journal projection

testing/projections/build.gradle

@@ -13,5 +13,6 @@ dependencies {
     testImplementation(project(":core:kernel"))
     testImplementation(project(":core:artifacts"))
     testImplementation(project(":core:router"))
+    testImplementation(project(":core:journal"))
     implementation(project(":testing:fixtures"))
 }

testing/projections/src/test/kotlin/DecisionJournalProjectorTest.kt

@@ -0,0 +1,47 @@
+import com.correx.core.events.events.SteeringNoteAddedEvent
+import com.correx.core.events.events.TransitionExecutedEvent
+import com.correx.core.events.types.SessionId
+import com.correx.core.events.types.StageId
+import com.correx.core.events.types.TransitionId
+import com.correx.core.journal.DecisionJournalProjector
+import com.correx.core.journal.DefaultDecisionJournalReducer
+import com.correx.core.journal.model.DecisionKind
+import com.correx.testing.fixtures.EventFixtures.stored
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class DecisionJournalProjectorTest {
+    private val projector = DecisionJournalProjector(DefaultDecisionJournalReducer())
+
+    @Test
+    fun `steering and transition each produce one ordered record`() {
+        var s = projector.initial()
+        s = projector.apply(
+            s,
+            stored(
+                payload = SteeringNoteAddedEvent(SessionId("x"), "use jwt", StageId("plan")),
+                sequence = 1L,
+            ),
+        )
+        s = projector.apply(
+            s,
+            stored(
+                payload = TransitionExecutedEvent(SessionId("x"), StageId("plan"), StageId("impl"), TransitionId("t1")),
+                sequence = 2L,
+            ),
+        )
+        assertEquals(2, s.records.size)
+        assertEquals(DecisionKind.STEERING, s.records[0].kind)
+        assertEquals(DecisionKind.TRANSITION, s.records[1].kind)
+    }
+
+    @Test
+    fun `unrelated events are ignored`() {
+        val s0 = projector.initial()
+        val s1 = projector.apply(
+            s0,
+            stored(payload = SteeringNoteAddedEvent(SessionId("x"), "note")),
+        )
+        assertEquals(1, s1.records.size)
+    }
+}