crates/irtt-cli/src/cmd/client/args.rs

@@ -1,12 +1,10 @@
 use std::time::Duration;
 
-use clap::{Parser, ValueEnum};
-use irtt_client::ClientConfig;
-
 use crate::shared::client::{
-    parse_labelled_target, parse_test_duration, prepare_managed_targets, target_specs,
-    CommonClientArgs, GroupPacingArg, LabelledTargetArg, PreparedTarget, TargetSpec, TimestampArg,
+    parse_labelled_target, parse_test_duration, prepare_managed_run, CommonClientArgs,
+    GroupPacingArg, LabelledTargetArg, ManagedRunSetup, TargetSelection, TimestampArg,
 };
+use clap::{Parser, ValueEnum};
 
 pub const DEFAULT_CLIENT_DURATION: Duration = Duration::from_secs(10);
 
@@ -91,11 +89,19 @@ pub struct ClientArgs {
 }
 
 impl ClientArgs {
-    pub fn to_client_config(&self) -> ClientConfig {
-        self.common.to_client_config(
-            self.primary_target_addr()
-                .expect("target is required unless --list-columns is set"),
+    /// Validate the selected targets and prepare the managed run.
+    ///
+    /// Targets are only required here. `--list-columns` returns before this is
+    /// called, so listing columns still needs no target.
+    pub fn prepare(&self) -> Result<ManagedRunSetup, String> {
+        prepare_managed_run(
+            &self.common,
             self.duration,
+            TargetSelection {
+                positional: &self.targets,
+                labelled: &self.labelled_targets,
+                pacing: self.pacing,
+            },
         )
     }
 
@@ -106,22 +112,6 @@ impl ClientArgs {
     pub fn timestamp_mode(&self) -> TimestampArg {
         self.common.tstamp
     }
-
-    pub fn target_specs(&self) -> Result<Vec<CliTargetSpec>, String> {
-        target_specs(&self.targets, &self.labelled_targets)
-    }
-
-    pub fn managed_targets(&self) -> Result<Vec<CliManagedTarget>, String> {
-        prepare_managed_targets(self.target_specs()?)
-    }
-
-    fn primary_target_addr(&self) -> Option<&str> {
-        self.targets.first().map(String::as_str).or_else(|| {
-            self.labelled_targets
-                .first()
-                .map(|target| target.addr.as_str())
-        })
-    }
 }
 
 impl std::ops::Deref for ClientArgs {
@@ -144,9 +134,6 @@ pub enum OutputFormat {
     Jsonl,
 }
 
-pub type CliTargetSpec = TargetSpec;
-pub type CliManagedTarget = PreparedTarget;
-
 impl OutputFormat {
     pub fn prints_summary(self) -> bool {
         matches!(self, Self::Table)
@@ -191,7 +178,7 @@ mod tests {
         assert!(!args.is_continuous());
         assert_eq!(args.timestamp_mode(), TimestampArg::Both);
 
-        let config = args.to_client_config();
+        let config = args.prepare().unwrap().client;
         assert_eq!(config.duration, Some(DEFAULT_CLIENT_DURATION));
         assert_eq!(config.received_stats, ReceivedStats::Both);
         assert_eq!(config.stamp_at, StampAt::Both);
@@ -212,17 +199,22 @@ mod tests {
         let args = parse(&["--list-columns"]).unwrap();
         assert!(args.targets.is_empty());
         assert!(args.list_columns);
+        // The parser accepts no target; preparation is where a target becomes
+        // mandatory, and the stream command returns before preparing when
+        // listing columns.
+        let err = args.prepare().unwrap_err();
+        assert!(err.contains("--list-columns"));
     }
 
     #[test]
     fn multiple_positional_targets_parse_as_targets() {
         let args = parse(&["host-a:2112", "host-b:2112"]).unwrap();
-        let specs = args.target_specs().unwrap();
+        let specs = args.prepare().unwrap().targets;
 
         assert_eq!(specs[0].label, "host-a:2112");
-        assert_eq!(specs[0].addr, "host-a:2112");
+        assert_eq!(specs[0].managed.server_addr, "host-a:2112");
         assert_eq!(specs[1].label, "host-b:2112");
-        assert_eq!(specs[1].addr, "host-b:2112");
+        assert_eq!(specs[1].managed.server_addr, "host-b:2112");
     }
 
     #[test]
@@ -234,18 +226,18 @@ mod tests {
             "sg=sg.example.com:2112",
         ])
         .unwrap();
-        let specs = args.target_specs().unwrap();
+        let specs = args.prepare().unwrap().targets;
 
         assert_eq!(specs[0].label, "ams");
-        assert_eq!(specs[0].addr, "ams.example.com:2112");
+        assert_eq!(specs[0].managed.server_addr, "ams.example.com:2112");
         assert_eq!(specs[1].label, "sg");
-        assert_eq!(specs[1].addr, "sg.example.com:2112");
+        assert_eq!(specs[1].managed.server_addr, "sg.example.com:2112");
     }
 
     #[test]
     fn duplicate_labels_are_rejected() {
         let args = parse(&["host-a:2112", "--target", "host-a:2112=host-b:2112"]).unwrap();
-        let err = args.target_specs().unwrap_err();
+        let err = args.prepare().unwrap_err();
 
         assert!(err.contains("duplicate target label"));
     }
@@ -253,7 +245,7 @@ mod tests {
     #[test]
     fn duplicate_positional_target_strings_get_stable_suffixes() {
         let args = parse(&["host-a:2112", "host-a:2112"]).unwrap();
-        let specs = args.target_specs().unwrap();
+        let specs = args.prepare().unwrap().targets;
 
         assert_eq!(specs[0].label, "host-a:2112");
         assert_eq!(specs[1].label, "host-a:2112#2");
@@ -262,7 +254,7 @@ mod tests {
     #[test]
     fn duplicate_target_endpoints_are_allowed() {
         let args = parse(&["127.0.0.1:2112", "127.0.0.1"]).unwrap();
-        assert_eq!(args.managed_targets().unwrap().len(), 2);
+        assert_eq!(args.prepare().unwrap().target_count(), 2);
     }
 
     #[test]

crates/irtt-cli/src/cmd/client/run.rs

@@ -9,9 +9,8 @@ use std::{
 
 use irtt_client::{
     managed::{
-        BlockingManagedClient, ManagedClientConfig, ManagedCompletionPolicy, ManagedEndReason,
-        ManagedEvent, ManagedEventSubscription, ManagedEventTryRecvError, ManagedTargetEndReason,
-        ManagedTargetOutcome, TargetInstance,
+        BlockingManagedClient, ManagedEndReason, ManagedEvent, ManagedEventSubscription,
+        ManagedEventTryRecvError, ManagedTargetEndReason, ManagedTargetOutcome, TargetInstance,
     },
     ClientEvent,
 };
@@ -44,7 +43,6 @@ const FINITE_STATS_MEMORY_STRONG_WARNING_BYTES: u64 = 512 * MIB;
 
 const FINITE_STATS_MEMORY_VERY_STRONG_WARNING_BYTES: u64 = GIB;
 const MANAGED_EVENT_WAIT_SLICE: Duration = Duration::from_millis(20);
-const MANAGED_EVENT_CAPACITY: usize = 16_384;
 
 pub fn run_stream(
     args: ClientArgs,
@@ -54,10 +52,10 @@ pub fn run_stream(
         print!("{}", OutputConfig::list_columns());
         return Ok(());
     }
-    let targets = args
-        .managed_targets()
+    let setup = args
+        .prepare()
         .map_err(|err| io::Error::new(io::ErrorKind::InvalidInput, err))?;
-    let multi_target = targets.len() > 1;
+    let multi_target = setup.is_multi_target();
     let output_config = OutputConfig::new(
         args.format,
         args.columns.as_deref(),
@@ -67,7 +65,7 @@ pub fn run_stream(
     )
     .map_err(|err| io::Error::new(io::ErrorKind::InvalidInput, err))?;
     let continuous = args.is_continuous();
-    let target_count = targets.len();
+    let target_count = setup.target_count();
 
     if let Some(warning) = finite_stats_memory_warning(&args, target_count) {
         eprintln!("{warning}");
@@ -75,21 +73,9 @@ pub fn run_stream(
     if is_shutdown_requested(shutdown_requested) {
         return Ok(());
     }
-    let config = ManagedClientConfig {
-        client: args.to_client_config(),
-        pacing: args.pacing.into(),
-        completion: ManagedCompletionPolicy::FinishWhenQuiescent,
-        event_capacity: MANAGED_EVENT_CAPACITY,
-        outcome_history_limit: target_count,
-        max_live_target_generations: target_count,
-        ..ManagedClientConfig::default()
-    };
     let (owner, mut events) = BlockingManagedClient::start_with_subscription(
-        config,
-        targets
-            .iter()
-            .map(|target| target.managed.clone())
-            .collect(),
+        setup.managed_config(),
+        setup.managed_targets(),
     )?;
     let handle = owner.handle();
     let mut stdout = io::LineWriter::new(io::stdout().lock());
@@ -101,7 +87,8 @@ pub fn run_stream(
         out: &mut stdout,
     };
 
-    let mut stats = targets
+    let mut stats = setup
+        .targets
         .iter()
         .map(|target| {
             (

crates/irtt-cli/src/cmd/tui/args.rs

@@ -1,13 +1,12 @@
 use std::time::Duration;
 
 use clap::Parser;
-use irtt_client::ClientConfig;
 
 #[cfg(test)]
 use crate::shared::client::TimestampArg;
 use crate::shared::client::{
-    parse_labelled_target, parse_test_duration, prepare_managed_targets, target_specs,
-    CommonClientArgs, GroupPacingArg, LabelledTargetArg, PreparedTarget, TargetSpec,
+    parse_labelled_target, parse_test_duration, prepare_managed_run, CommonClientArgs,
+    GroupPacingArg, LabelledTargetArg, ManagedRunSetup, TargetSelection,
 };
 
 pub const DEFAULT_TUI_DURATION: Duration = Duration::ZERO;
@@ -56,11 +55,19 @@ pub struct TuiArgs {
 }
 
 impl TuiArgs {
-    pub fn to_client_config(&self) -> ClientConfig {
-        self.common.to_client_config(
-            self.primary_target_addr()
-                .expect("at least one target is required"),
+    /// Validate the selected targets and prepare the managed run.
+    ///
+    /// The TUI always requires a target: the parser rejects an empty target
+    /// list, and this rejects a target set that cannot be labelled uniquely.
+    pub fn prepare(&self) -> Result<ManagedRunSetup, String> {
+        prepare_managed_run(
+            &self.common,
             self.duration,
+            TargetSelection {
+                positional: &self.targets,
+                labelled: &self.labelled_targets,
+                pacing: self.pacing,
+            },
         )
     }
 
@@ -68,31 +75,12 @@ impl TuiArgs {
         self.duration == Duration::ZERO
     }
 
-    pub fn target_specs(&self) -> Result<Vec<TuiTargetSpec>, String> {
-        target_specs(&self.targets, &self.labelled_targets)
-    }
-
-    pub fn managed_targets(&self) -> Result<Vec<TuiManagedTarget>, String> {
-        prepare_managed_targets(self.target_specs()?)
-    }
-
     #[cfg(test)]
     pub fn timestamp_mode(&self) -> TimestampArg {
         self.common.tstamp
     }
-
-    fn primary_target_addr(&self) -> Option<&str> {
-        self.targets.first().map(String::as_str).or_else(|| {
-            self.labelled_targets
-                .first()
-                .map(|target| target.addr.as_str())
-        })
-    }
 }
 
-pub type TuiTargetSpec = TargetSpec;
-pub type TuiManagedTarget = PreparedTarget;
-
 impl std::ops::Deref for TuiArgs {
     type Target = CommonClientArgs;
 
@@ -132,12 +120,12 @@ mod tests {
         assert_eq!(args.pacing, GroupPacingArg::Staggered);
         assert_eq!(args.duration, DEFAULT_TUI_DURATION);
         assert!(args.is_continuous());
-        assert_eq!(args.to_client_config().duration, None);
+        assert_eq!(args.prepare().unwrap().client.duration, None);
 
         let finite = parse(&["--duration", "30s", "127.0.0.1:2112"]).unwrap();
         assert_eq!(finite.duration, Duration::from_secs(30));
         assert_eq!(
-            finite.to_client_config().duration,
+            finite.prepare().unwrap().client.duration,
             Some(Duration::from_secs(30))
         );
 
@@ -149,12 +137,12 @@ mod tests {
     #[test]
     fn multiple_positional_targets_parse() {
         let args = parse(&["host-a:2112", "host-b:2112"]).unwrap();
-        let specs = args.target_specs().unwrap();
+        let specs = args.prepare().unwrap().targets;
 
         assert_eq!(specs[0].label, "host-a:2112");
-        assert_eq!(specs[0].addr, "host-a:2112");
+        assert_eq!(specs[0].managed.server_addr, "host-a:2112");
         assert_eq!(specs[1].label, "host-b:2112");
-        assert_eq!(specs[1].addr, "host-b:2112");
+        assert_eq!(specs[1].managed.server_addr, "host-b:2112");
     }
 
     #[test]
@@ -166,23 +154,26 @@ mod tests {
             "sg=sg.example.com:2112",
         ])
         .unwrap();
-        let specs = args.target_specs().unwrap();
+        let specs = args.prepare().unwrap().targets;
 
         assert_eq!(specs[0].label, "ams");
-        assert_eq!(specs[0].addr, "ams.example.com:2112");
+        assert_eq!(specs[0].managed.server_addr, "ams.example.com:2112");
         assert_eq!(specs[1].label, "sg");
-        assert_eq!(specs[1].addr, "sg.example.com:2112");
+        assert_eq!(specs[1].managed.server_addr, "sg.example.com:2112");
     }
 
     #[test]
     fn at_least_one_target_is_required() {
+        // The TUI has no target-free mode, so this is rejected at parse time
+        // rather than during preparation.
         assert!(parse(&[]).is_err());
+        assert!(parse(&["--target", "ams=ams.example.com:2112"]).is_ok());
     }
 
     #[test]
     fn duplicate_labels_are_rejected() {
         let args = parse(&["host-a:2112", "--target", "host-a:2112=host-b:2112"]).unwrap();
-        let err = args.target_specs().unwrap_err();
+        let err = args.prepare().unwrap_err();
 
         assert!(err.contains("duplicate target label"));
     }
@@ -190,7 +181,7 @@ mod tests {
     #[test]
     fn duplicate_positional_target_strings_get_stable_suffixes() {
         let args = parse(&["host-a:2112", "host-a:2112"]).unwrap();
-        let specs = args.target_specs().unwrap();
+        let specs = args.prepare().unwrap().targets;
 
         assert_eq!(specs[0].label, "host-a:2112");
         assert_eq!(specs[1].label, "host-a:2112#2");
@@ -199,7 +190,7 @@ mod tests {
     #[test]
     fn duplicate_target_endpoints_are_allowed() {
         let args = parse(&["127.0.0.1:2112", "127.0.0.1"]).unwrap();
-        assert_eq!(args.managed_targets().unwrap().len(), 2);
+        assert_eq!(args.prepare().unwrap().target_count(), 2);
     }
 
     #[test]
@@ -272,11 +263,10 @@ mod tests {
             "--loose",
             "127.0.0.1:2112",
         ];
-        let tui = parse(&tui_args).unwrap().to_client_config();
+        let tui = parse(&tui_args).unwrap().prepare().unwrap().client;
         let common = parse_shared(&shared).unwrap().common;
-        let shared = common.to_client_config("127.0.0.1:2112", Duration::from_secs(30));
+        let shared = common.to_client_config(Duration::from_secs(30));
 
-        assert_eq!(shared.server_addr, tui.server_addr);
         assert_eq!(shared.duration, tui.duration);
         assert_eq!(shared.interval, tui.interval);
         assert_eq!(shared.length, tui.length);

crates/irtt-cli/src/cmd/tui/run.rs

@@ -19,27 +19,26 @@ use crate::{
 };
 use crossterm::event::{self, Event, KeyCode, KeyEventKind, KeyModifiers};
 use irtt_client::managed::{
-    BlockingManagedClient, ManagedClientConfig, ManagedCompletionPolicy, ManagedEndReason,
-    ManagedEvent, ManagedEventSubscription, ManagedEventTryRecvError, TargetInstance,
+    BlockingManagedClient, ManagedEndReason, ManagedEvent, ManagedEventSubscription,
+    ManagedEventTryRecvError, TargetInstance,
 };
 
 const RENDER_INTERVAL: Duration = Duration::from_millis(250);
 const TUI_WAIT_SLICE: Duration = Duration::from_millis(20);
-const MANAGED_EVENT_CAPACITY: usize = 16_384;
 const INPUT_EVENT_WORK_BUDGET: usize = 128;
 
 pub fn run_tui(
     args: TuiArgs,
     shutdown_requested: &AtomicBool,
 ) -> Result<(), Box<dyn std::error::Error>> {
-    let targets = args
-        .managed_targets()
+    let setup = args
+        .prepare()
         .map_err(|err| io::Error::new(io::ErrorKind::InvalidInput, err))?;
     let continuous = args.is_continuous();
     let mut terminal = TuiTerminal::enter()?;
     let mut state = TuiState::with_target_labels(
-        TuiConfig::from_args(&args),
-        targets.iter().map(|target| target.label.clone()),
+        TuiConfig::from_args(&args, &setup),
+        setup.targets.iter().map(|target| target.label.clone()),
     );
     let mut next_render = Instant::now();
     if is_shutdown_requested(shutdown_requested) {
@@ -47,22 +46,9 @@ pub fn run_tui(
     }
     state.set_status(TuiStatus::Opening);
     render_if_due(&mut terminal, &state, &mut next_render, true)?;
-    let target_count = targets.len();
-    let config = ManagedClientConfig {
-        client: args.to_client_config(),
-        pacing: args.pacing.into(),
-        completion: ManagedCompletionPolicy::FinishWhenQuiescent,
-        event_capacity: MANAGED_EVENT_CAPACITY,
-        outcome_history_limit: target_count,
-        max_live_target_generations: target_count,
-        ..ManagedClientConfig::default()
-    };
     let (owner, mut events) = match BlockingManagedClient::start_with_subscription(
-        config,
-        targets
-            .iter()
-            .map(|target| target.managed.clone())
-            .collect(),
+        setup.managed_config(),
+        setup.managed_targets(),
     ) {
         Ok(value) => value,
         Err(error) => {

crates/irtt-cli/src/cmd/tui/ui.rs

@@ -30,7 +30,7 @@ use crate::{
         },
         tui::args::TuiArgs,
     },
-    shared::client::{expected_probe_count, GroupPacingArg},
+    shared::client::{expected_probe_count, GroupPacingArg, ManagedRunSetup},
 };
 
 const HISTORY_LIMIT: usize = 100_000;
@@ -656,11 +656,11 @@ pub(super) struct TuiConfig {
 }
 
 impl TuiConfig {
-    pub(super) fn from_args(args: &TuiArgs) -> Self {
+    pub(super) fn from_args(args: &TuiArgs, setup: &ManagedRunSetup) -> Self {
         Self {
             interval: args.interval,
             duration: (!args.is_continuous()).then_some(args.duration),
-            timeout: args.to_client_config().probe_timeout,
+            timeout: setup.client.probe_timeout,
             target_probes: (!args.is_continuous())
                 .then(|| expected_probe_count(args.duration, args.interval)),
             pacing: args.pacing,

crates/irtt-cli/src/shared/client/config.rs

@@ -7,9 +7,13 @@ use super::args::CommonClientArgs;
 pub const DEFAULT_RECV_TIMEOUT: Duration = Duration::from_millis(20);
 
 impl CommonClientArgs {
-    pub fn to_client_config(&self, server: &str, duration: Duration) -> ClientConfig {
+    /// Build the shared client configuration template for a managed run.
+    ///
+    /// The template carries no server address: the managed driver replaces it
+    /// per target from that target's configuration, so deriving one here from
+    /// an arbitrary target would be dead data.
+    pub fn to_client_config(&self, duration: Duration) -> ClientConfig {
         ClientConfig {
-            server_addr: server.to_owned(),
             duration: (!duration.is_zero()).then_some(duration),
             interval: self.interval,
             length: self.length,

crates/irtt-cli/src/shared/client/mod.rs

@@ -1,5 +1,6 @@
 pub mod args;
 pub mod config;
+pub mod prepare;
 pub mod session;
 pub mod targets;
 
@@ -8,6 +9,7 @@ pub use args::{
     ClockArg, CommonClientArgs, ReceivedStatsArg, TimestampArg,
 };
 pub use config::{expected_probe_count, DEFAULT_RECV_TIMEOUT};
+pub use prepare::{prepare_managed_run, ManagedRunSetup, TargetSelection, MANAGED_EVENT_CAPACITY};
 pub use session::is_shutdown_requested;
 pub use targets::{
     parse_labelled_target, prepare_managed_targets, target_specs, GroupPacingArg,

crates/irtt-cli/src/shared/client/prepare.rs

@@ -0,0 +1,258 @@
+//! One preparation step from parsed arguments to a runnable managed setup.
+//!
+//! Both client applets accept the same target and pacing arguments and then
+//! have to turn them into the same three things: a validated target set, one
+//! shared [`ClientConfig`] template, and a [`ManagedPacing`]. Doing that
+//! separately in each applet is how the CLI ended up deriving its client
+//! configuration from an arbitrary "primary" target whose address the managed
+//! driver immediately replaced per target.
+
+use std::time::Duration;
+
+use irtt_client::{
+    managed::{ManagedClientConfig, ManagedCompletionPolicy, ManagedPacing},
+    ClientConfig,
+};
+
+use super::{
+    args::CommonClientArgs,
+    targets::{prepare_managed_targets, target_specs, GroupPacingArg, LabelledTargetArg},
+    PreparedTarget,
+};
+
+/// Capacity of the lossy managed presentation event channel.
+pub const MANAGED_EVENT_CAPACITY: usize = 16_384;
+
+/// Target and pacing arguments common to the client applets.
+///
+/// Duration is deliberately absent: the applets disagree about what a duration
+/// means and what its default is, so each keeps its own.
+#[derive(Debug, Clone, Copy)]
+pub struct TargetSelection<'a> {
+    pub positional: &'a [String],
+    pub labelled: &'a [LabelledTargetArg],
+    pub pacing: GroupPacingArg,
+}
+
+/// Everything a managed run needs, prepared and validated together.
+#[derive(Debug, Clone)]
+pub struct ManagedRunSetup {
+    /// Validated targets, in the order the user gave them.
+    pub targets: Vec<PreparedTarget>,
+    /// Shared client configuration template.
+    ///
+    /// The managed driver supplies each target's address and authentication
+    /// from its [`ManagedTargetConfig`](irtt_client::managed::ManagedTargetConfig),
+    /// so this template carries no target of its own.
+    pub client: ClientConfig,
+    /// Send coordination across active targets.
+    pub pacing: ManagedPacing,
+}
+
+impl ManagedRunSetup {
+    /// Number of validated targets.
+    pub fn target_count(&self) -> usize {
+        self.targets.len()
+    }
+
+    /// Whether this run drives more than one target.
+    pub fn is_multi_target(&self) -> bool {
+        self.targets.len() > 1
+    }
+
+    /// Managed target configurations, in argument order.
+    pub fn managed_targets(&self) -> Vec<irtt_client::managed::ManagedTargetConfig> {
+        self.targets
+            .iter()
+            .map(|target| target.managed.clone())
+            .collect()
+    }
+
+    /// Managed driver configuration for this run.
+    pub fn managed_config(&self) -> ManagedClientConfig {
+        let target_count = self.target_count();
+        ManagedClientConfig {
+            client: self.client.clone(),
+            pacing: self.pacing,
+            completion: ManagedCompletionPolicy::FinishWhenQuiescent,
+            event_capacity: MANAGED_EVENT_CAPACITY,
+            outcome_history_limit: target_count,
+            max_live_target_generations: target_count,
+            ..ManagedClientConfig::default()
+        }
+    }
+}
+
+/// Validate the selected targets and build the shared run setup.
+///
+/// Targets are validated before any configuration is built, so a bad target set
+/// fails before the caller can act on a half-prepared run.
+pub fn prepare_managed_run(
+    common: &CommonClientArgs,
+    duration: Duration,
+    selection: TargetSelection<'_>,
+) -> Result<ManagedRunSetup, String> {
+    let specs = target_specs(selection.positional, selection.labelled)?;
+    let targets = prepare_managed_targets(specs)?;
+    Ok(ManagedRunSetup {
+        targets,
+        client: common.to_client_config(duration),
+        pacing: selection.pacing.into(),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use clap::Parser;
+
+    use super::*;
+
+    #[derive(Parser)]
+    struct CommonOnlyArgs {
+        #[command(flatten)]
+        common: CommonClientArgs,
+    }
+
+    fn common(args: &[&str]) -> CommonClientArgs {
+        let mut argv = vec!["common-only"];
+        argv.extend_from_slice(args);
+        CommonOnlyArgs::try_parse_from(argv).unwrap().common
+    }
+
+    fn prepare(
+        positional: &[&str],
+        labelled: &[LabelledTargetArg],
+        pacing: GroupPacingArg,
+        duration: Duration,
+    ) -> Result<ManagedRunSetup, String> {
+        let positional: Vec<String> = positional.iter().map(|value| (*value).to_owned()).collect();
+        prepare_managed_run(
+            &common(&[]),
+            duration,
+            TargetSelection {
+                positional: &positional,
+                labelled,
+                pacing,
+            },
+        )
+    }
+
+    #[test]
+    fn a_single_target_prepares_one_managed_target_and_a_finite_duration() {
+        let setup = prepare(
+            &["127.0.0.1:2112"],
+            &[],
+            GroupPacingArg::Staggered,
+            Duration::from_secs(30),
+        )
+        .unwrap();
+
+        assert_eq!(setup.target_count(), 1);
+        assert!(!setup.is_multi_target());
+        assert_eq!(setup.targets[0].label, "127.0.0.1:2112");
+        assert_eq!(setup.targets[0].managed.server_addr, "127.0.0.1:2112");
+        assert_eq!(setup.client.duration, Some(Duration::from_secs(30)));
+        assert_eq!(setup.pacing, ManagedPacing::Staggered);
+    }
+
+    #[test]
+    fn a_zero_duration_prepares_a_continuous_client_config() {
+        let setup = prepare(
+            &["127.0.0.1:2112"],
+            &[],
+            GroupPacingArg::Staggered,
+            Duration::ZERO,
+        )
+        .unwrap();
+
+        assert_eq!(setup.client.duration, None);
+    }
+
+    #[test]
+    fn multiple_targets_keep_argument_order_and_share_one_client_config() {
+        let labelled = vec![LabelledTargetArg {
+            label: "sg".to_owned(),
+            addr: "sg.example.test:2112".to_owned(),
+        }];
+        let setup = prepare(
+            &["host-a:2112", "host-b:2112"],
+            &labelled,
+            GroupPacingArg::Burst,
+            Duration::from_secs(10),
+        )
+        .unwrap();
+
+        assert!(setup.is_multi_target());
+        let labels: Vec<_> = setup
+            .targets
+            .iter()
+            .map(|target| target.label.as_str())
+            .collect();
+        assert_eq!(labels, ["host-a:2112", "host-b:2112", "sg"]);
+        assert_eq!(setup.targets[2].managed.server_addr, "sg.example.test:2112");
+        assert_eq!(setup.pacing, ManagedPacing::Burst);
+
+        let config = setup.managed_config();
+        assert_eq!(config.outcome_history_limit, 3);
+        assert_eq!(config.max_live_target_generations, 3);
+        assert_eq!(config.event_capacity, MANAGED_EVENT_CAPACITY);
+        assert_eq!(config.pacing, ManagedPacing::Burst);
+        assert_eq!(config.client, setup.client);
+        assert_eq!(setup.managed_targets().len(), 3);
+    }
+
+    #[test]
+    fn the_shared_client_config_carries_no_target_of_its_own() {
+        // The managed driver replaces the address, and the CLI's key, per
+        // target, so the template must not pin either to one target.
+        let positional = vec!["host-a:2112".to_owned(), "host-b:2112".to_owned()];
+        let setup = prepare_managed_run(
+            &common(&["--hmac", "secret"]),
+            Duration::from_secs(10),
+            TargetSelection {
+                positional: &positional,
+                labelled: &[],
+                pacing: GroupPacingArg::Staggered,
+            },
+        )
+        .unwrap();
+
+        assert_eq!(
+            setup.client.server_addr,
+            ClientConfig::default().server_addr
+        );
+        assert_eq!(setup.client.hmac_key, Some(b"secret".to_vec()));
+        // Per-target authentication is not exposed on the command line, so no
+        // target carries an override of the shared key.
+        assert!(setup
+            .targets
+            .iter()
+            .all(|target| target.managed.auth.is_none()));
+    }
+
+    #[test]
+    fn an_empty_target_set_is_rejected_with_the_list_columns_hint() {
+        let err =
+            prepare(&[], &[], GroupPacingArg::Staggered, Duration::from_secs(10)).unwrap_err();
+
+        assert!(err.contains("at least one target is required"));
+        assert!(err.contains("--list-columns"));
+    }
+
+    #[test]
+    fn a_duplicate_label_is_rejected_before_any_configuration_is_built() {
+        let labelled = vec![LabelledTargetArg {
+            label: "host-a:2112".to_owned(),
+            addr: "host-b:2112".to_owned(),
+        }];
+        let err = prepare(
+            &["host-a:2112"],
+            &labelled,
+            GroupPacingArg::Staggered,
+            Duration::from_secs(10),
+        )
+        .unwrap_err();
+
+        assert!(err.contains("duplicate target label"));
+    }
+}