diff --git a/cargo-nextest/src/cargo_cli.rs b/cargo-nextest/src/cargo_cli.rs
index 7a75ab35fdf..f83fb5da51a 100644
--- a/cargo-nextest/src/cargo_cli.rs
+++ b/cargo-nextest/src/cargo_cli.rs
@@ -6,6 +6,7 @@
 use crate::output::OutputContext;
 use camino::{Utf8Path, Utf8PathBuf};
 use clap::Args;
+use guppy::graph::PackageGraph;
 use std::path::PathBuf;
 
 /// Options passed down to cargo.
@@ -143,6 +144,19 @@ pub(crate) struct CargoOptions {
     unstable_flags: Vec<String>,
 }
 
+impl CargoOptions {
+    fn needs_default_members_warning(&self, graph: &PackageGraph) -> bool {
+        // If any package-related options are passed in, don't produce a warning.
+        if !self.packages.is_empty() || self.workspace || self.all {
+            return false;
+        }
+
+        // TODO: figure out whether this will cause everything to be built. Factors to consider:
+        // * symlinks
+        // * exact behavior with nested directories
+    }
+}
+
 #[derive(Clone, Debug)]
 pub(crate) struct CargoCli<'a> {
     cargo_path: Utf8PathBuf,
diff --git a/nextest-runner/src/cargo_toml.rs b/nextest-runner/src/cargo_toml.rs
new file mode 100644
index 00000000000..57f9cad21a6
--- /dev/null
+++ b/nextest-runner/src/cargo_toml.rs
@@ -0,0 +1,49 @@
+// Copyright (c) The nextest Contributors
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+//! Support for reading `Cargo.toml` files.
+//!
+//! This package contains logic to partially read and understand `Cargo.toml` files: just enough for
+//! nextest's needs.
+
+use crate::errors::RootCargoTomlError;
+use camino::{Utf8Path, Utf8PathBuf};
+use serde::Deserialize;
+
+/// Represents a workspace's root Cargo.toml.
+#[derive(Clone, Debug, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub struct RootCargoToml {
+    /// The workspace key.
+    pub workspace: RootCargoTomlWorkspace,
+}
+
+impl RootCargoToml {
+    /// Reads the root Cargo.toml into this file.
+    pub fn read_file(path: &Utf8Path) -> Result<Self, RootCargoTomlError> {
+        let contents =
+            std::fs::read_to_string(&path).map_err(|error| RootCargoTomlError::ReadError {
+                path: path.to_owned(),
+                error,
+            })?;
+
+        toml_edit::easy::from_str(&contents).map_err(|error| RootCargoTomlError::ParseError {
+            path: path.to_owned(),
+            error,
+        })
+    }
+
+    /// Returns true if the workspace has default members.
+    pub fn has_default_members(&self) -> bool {
+        self.workspace.default_members.is_some()
+    }
+}
+
+/// The `[workspace]` section of a [`RootCargoToml`].
+#[derive(Clone, Debug, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub struct RootCargoTomlWorkspace {
+    /// The default members of the workspace.
+    #[serde(default)]
+    pub default_members: Option<Vec<Utf8PathBuf>>,
+}
diff --git a/nextest-runner/src/errors.rs b/nextest-runner/src/errors.rs
index 4a52f5b0e53..e82e2c97437 100644
--- a/nextest-runner/src/errors.rs
+++ b/nextest-runner/src/errors.rs
@@ -863,6 +863,32 @@ pub enum CargoConfigError {
     },
 }
 
+/// An error occurred while parsing a root Cargo.toml.
+#[derive(Debug, Error)]
+pub enum RootCargoTomlError {
+    /// Error reading a file from disk.
+    #[error("failed to read workspace `{path}`")]
+    ReadError {
+        /// The path to the file.
+        path: Utf8PathBuf,
+
+        /// The inner error.
+        #[source]
+        error: std::io::Error,
+    },
+
+    /// Error parsing the `Cargo.toml` file.
+    #[error("failed to parse workspace `{path}`")]
+    ParseError {
+        /// The path to the file.
+        path: Utf8PathBuf,
+
+        /// The error that occurred trying to deserialize the file.
+        #[source]
+        error: toml_edit::easy::de::Error,
+    },
+}
+
 /// The reason an invalid CLI config failed.
 ///
 /// Part of [`CargoConfigError::InvalidCliConfig`].
diff --git a/nextest-runner/src/lib.rs b/nextest-runner/src/lib.rs
index bebe0945307..e72a4e083d3 100644
--- a/nextest-runner/src/lib.rs
+++ b/nextest-runner/src/lib.rs
@@ -10,6 +10,7 @@
 //! post](https://sunshowers.io/posts/nextest-and-tokio/).
 
 pub mod cargo_config;
+pub mod cargo_toml;
 pub mod config;
 #[cfg(feature = "experimental-tokio-console")]
 pub mod console;