diff --git a/Cargo.lock b/Cargo.lock
index cc561874ac..0cf86496b5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5273,6 +5273,12 @@ version = "0.68.0"
 dependencies = [
  "anyhow",
  "bytes",
+ "decaf377-rdsa",
+ "ed25519-consensus",
+ "penumbra-keys",
+ "penumbra-proto",
+ "rand 0.8.5",
+ "rand_core 0.6.4",
  "serde_json",
  "tap",
  "tendermint",
diff --git a/crates/core/app/tests/common/mod.rs b/crates/core/app/tests/common/mod.rs
index f400c349fb..91798d7d16 100644
--- a/crates/core/app/tests/common/mod.rs
+++ b/crates/core/app/tests/common/mod.rs
@@ -3,15 +3,19 @@
 // NB: Allow dead code, these are in fact shared by files in `tests/`.
 #![allow(dead_code)]
 
-use async_trait::async_trait;
-use cnidarium::TempStorage;
-use penumbra_app::{
-    app::App,
-    server::consensus::{Consensus, ConsensusService},
+use {
+    async_trait::async_trait,
+    cnidarium::TempStorage,
+    penumbra_app::{
+        app::App,
+        server::consensus::{Consensus, ConsensusService},
+    },
+    penumbra_genesis::AppState,
+    penumbra_mock_consensus::TestNode,
+    std::ops::Deref,
+    tap::Tap,
+    tracing::{trace, warn},
 };
-use penumbra_genesis::AppState;
-use penumbra_mock_consensus::TestNode;
-use std::ops::Deref;
 
 // Installs a tracing subscriber to log events until the returned guard is dropped.
 pub fn set_tracing_subscriber() -> tracing::subscriber::DefaultGuard {
@@ -83,19 +87,63 @@ impl TempStorageExt for TempStorage {
 
 /// Penumbra-specific extensions to the mock consensus builder.
 pub trait BuilderExt: Sized {
+    /// The error thrown by [`with_penumbra_auto_app_state`]
     type Error;
+    /// Add the provided Penumbra [`AppState`] to the builder.
+    ///
+    /// This will inject any configured validators into the state before serializing it into bytes.
     fn with_penumbra_auto_app_state(self, app_state: AppState) -> Result<Self, Self::Error>;
 }
 
 impl BuilderExt for penumbra_mock_consensus::builder::Builder {
     type Error = anyhow::Error;
     fn with_penumbra_auto_app_state(self, app_state: AppState) -> Result<Self, Self::Error> {
-        // what to do here?
-        // - read out list of abci/comet validators from the builder,
-        // - define a penumbra validator for each one
-        // - inject that into the penumbra app state
-        // - serialize to json and then call `with_app_state_bytes`
-        let app_state = serde_json::to_vec(&app_state)?;
-        Ok(self.app_state(app_state))
+        use penumbra_proto::penumbra::core::component::stake::v1 as pb;
+
+        // Take the list of genesis validators from the builder...
+        let validators = self
+            .validators
+            .iter()
+            .inspect(
+                |pb::Validator {
+                     name,
+                     enabled,
+                     sequence_number,
+                     ..
+                 }| {
+                    // ...log the name of each...
+                    trace!(%name, %enabled, %sequence_number, "injecting validator into app state")
+                },
+            )
+            .cloned()
+            .collect::<Vec<_>>()
+            .tap(|v| {
+                // ...or print a warning if there are not any validators.
+                if v.is_empty() {
+                    warn!("`with_penumbra_auto_app_state` was called but builder has no validators")
+                }
+            });
+
+        // Add the validators to the app state.
+        let app_state: AppState = match app_state {
+            AppState::Checkpoint(_) => anyhow::bail!("checkpoint app state isn't supported"),
+            AppState::Content(mut content) => {
+                // Inject the builder's validators into the staking component's genesis state.
+                std::mem::replace(
+                        &mut content.stake_content.validators,
+                        validators
+                    )
+                    .tap(|overwritten| {
+                        // Log a warning if this overwrote any validators already in the app state.
+                        warn!(?overwritten, "`with_penumbra_auto_app_state` overwrote validators in the given AppState")
+                    });
+                AppState::Content(content)
+            }
+        };
+
+        // Serialize the app state into bytes, and add it to the builder.
+        serde_json::to_vec(&app_state)
+            .map_err(Self::Error::from)
+            .map(|s| self.app_state(s))
     }
 }
diff --git a/crates/core/app/tests/mock_consensus.rs b/crates/core/app/tests/mock_consensus.rs
index c68b8e3397..7b99ee63b0 100644
--- a/crates/core/app/tests/mock_consensus.rs
+++ b/crates/core/app/tests/mock_consensus.rs
@@ -3,6 +3,9 @@
 //  Note: these should eventually replace the existing test cases. mock consensus tests are placed
 //  here while the engine is still in development. See #3588.
 
+use penumbra_ibc::component::ClientStateReadExt;
+use penumbra_stake::component::validator_handler::ValidatorDataRead;
+
 mod common;
 
 use {
@@ -37,6 +40,24 @@ async fn mock_consensus_can_send_an_init_chain_request() -> anyhow::Result<()> {
     Ok(())
 }
 
+/// Exercises that the mock consensus engine can provide a single genesis validator.
+#[tokio::test]
+async fn mock_consensus_can_define_a_genesis_validator() -> anyhow::Result<()> {
+    // Install a test logger, acquire some temporary storage, and start the test node.
+    let guard = common::set_tracing_subscriber();
+    let storage = TempStorage::new().await?;
+    let test_node = common::start_test_node(&storage).await?;
+
+    let identity_key = test_node.identity_key;
+    storage.latest_snapshot().get_validator_status(identity_key);
+
+    // Free our temporary storage.
+    drop(storage);
+    drop(guard);
+
+    Ok(())
+}
+
 /// Exercises that a series of empty blocks, with no validator set present, can be successfully
 /// executed by the consensus service.
 #[tokio::test]
diff --git a/crates/test/mock-consensus/Cargo.toml b/crates/test/mock-consensus/Cargo.toml
index 5bbdd37521..d471fdefeb 100644
--- a/crates/test/mock-consensus/Cargo.toml
+++ b/crates/test/mock-consensus/Cargo.toml
@@ -10,6 +10,12 @@ license.workspace = true
 [dependencies]
 anyhow = { workspace = true }
 bytes = { workspace = true }
+decaf377-rdsa = { workspace = true }
+ed25519-consensus = { workspace = true }
+penumbra-proto = { workspace = true }
+penumbra-keys = { workspace = true }
+rand = {workspace = true}
+rand_core = {workspace = true}
 serde_json = { workspace = true }
 tap = { workspace = true }
 tendermint = { workspace = true }
diff --git a/crates/test/mock-consensus/src/builder.rs b/crates/test/mock-consensus/src/builder.rs
index 7d90e11c1f..1f74545bf2 100644
--- a/crates/test/mock-consensus/src/builder.rs
+++ b/crates/test/mock-consensus/src/builder.rs
@@ -5,12 +5,16 @@
 /// Most importantly, defines [`Builder::init_chain()`].
 mod init_chain;
 
-use {crate::TestNode, bytes::Bytes};
+use {
+    crate::TestNode, bytes::Bytes, penumbra_proto::penumbra::core::component::stake::v1 as pb,
+    rand_core::OsRng,
+};
 
 /// A buider, used to prepare and instantiate a new [`TestNode`].
 #[derive(Default)]
 pub struct Builder {
-    app_state: Option<Bytes>,
+    pub app_state: Option<Bytes>,
+    pub validators: Vec<pb::Validator>,
 }
 
 impl TestNode<()> {
@@ -21,12 +25,54 @@ impl TestNode<()> {
 }
 
 impl Builder {
-    // TODO: add other convenience methods for validator config?
-
     /// Creates a single validator with a randomly generated key.
     pub fn single_validator(self) -> Self {
-        // this does not do anything yet
-        self
+        use penumbra_proto::core::keys::v1::{GovernanceKey, IdentityKey};
+
+        // Generate a spend authoration key.
+        let bytes = {
+            use {
+                decaf377_rdsa::VerificationKey,
+                penumbra_keys::keys::{SpendKey, SpendKeyBytes},
+                rand::Rng,
+            };
+            let spend_key = SpendKey::from(SpendKeyBytes(OsRng.gen()));
+            let spend_auth_key = spend_key.spend_auth_key();
+            let verification_key = VerificationKey::from(spend_auth_key);
+            verification_key.to_bytes().to_vec()
+        };
+
+        // Generate an identity key for the validator.
+        let identity_key = Some(IdentityKey { ik: bytes.clone() });
+
+        // Generate a governance key for the validator.
+        //
+        // NB: for now, we will use the same key for governance. See the documentation of
+        // `GovernanceKey` for more information about cold storage of validator keys.
+        let governance_key = Some(GovernanceKey { gk: bytes.clone() });
+
+        // Generate a consensus pubkey for the validator.
+        let consensus_key = {
+            let signing_key = ed25519_consensus::SigningKey::new(OsRng);
+            signing_key.as_bytes().as_slice().to_vec()
+        };
+
+        let validator = pb::Validator {
+            identity_key,
+            consensus_key,
+            enabled: true,
+            sequence_number: 0,
+            governance_key,
+            name: String::default(),
+            website: String::default(),
+            description: String::default(),
+            funding_streams: Vec::default(),
+        };
+
+        Self {
+            validators: vec![validator],
+            ..self
+        }
     }
 
     /// Sets the `app_state_bytes` to send the ABCI application upon chain initialization.
diff --git a/crates/test/mock-consensus/src/builder/init_chain.rs b/crates/test/mock-consensus/src/builder/init_chain.rs
index b60a7793fd..93bbc23e97 100644
--- a/crates/test/mock-consensus/src/builder/init_chain.rs
+++ b/crates/test/mock-consensus/src/builder/init_chain.rs
@@ -32,6 +32,7 @@ impl Builder {
 
         let Self {
             app_state: Some(app_state),
+            validators: _,
         } = self
         else {
             bail!("builder was not fully initialized")