diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index adb6987..aa17b53 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -51,3 +51,105 @@ pub fn add_btreemap<E: Ord, T: Copy + std::ops::AddAssign>(
     });
     m1
 }
+
+/// A trait which indicates that it is possible to acquire a "placeholder" value
+/// of a type, which can be used for test purposes.
+#[cfg(test)]
+pub trait Placeholder : Sized {
+    /// Gets a placeholder value of this type which can be used for test purposes.
+    fn placeholder() -> Self;
+
+    /// Gets an array of placeholder values of this type which can be used for test purposes.
+    fn placeholder_array<const N: usize>() -> [Self; N] {
+        core::array::from_fn(|_| Self::placeholder())
+    }
+}
+
+/// A trait which indicates that it is possible to acquire a "placeholder" value
+/// of a type, which can be used for test purposes. These placeholder values are consistent
+/// across program runs.
+#[cfg(test)]
+pub trait PlaceholderSeed: Sized + PartialEq {
+    /// Gets a dummy valid of this type which can be used for test purposes.
+    ///
+    /// This allows acquiring multiple distinct placeholder values which are still consistent
+    /// between runs.
+    ///
+    /// ### Arguments
+    ///
+    /// * `seed_parts`  - the parts of the seed for the placeholder value to obtain. Two placeholder
+    ///                   values generated from the same seed are guaranteed to be equal (even
+    ///                   across multiple test runs, so long as the value format doesn't change).
+    fn placeholder_seed_parts<'a>(seed_parts: impl IntoIterator<Item = &'a [u8]>) -> Self;
+
+    /// Gets a dummy valid of this type which can be used for test purposes.
+    ///
+    /// This allows acquiring multiple distinct placeholder values which are still consistent
+    /// between runs.
+    ///
+    /// ### Arguments
+    ///
+    /// * `seed`  - the seed for the placeholder value to obtain. Two placeholder
+    ///             values generated from the same seed are guaranteed to be equal (even
+    ///             across multiple test runs, so long as the value format doesn't change).
+    fn placeholder_seed(seed: impl AsRef<[u8]>) -> Self {
+        Self::placeholder_seed_parts([ seed.as_ref() ])
+    }
+
+    /// Gets a dummy valid of this type which can be used for test purposes.
+    ///
+    /// This allows acquiring multiple distinct placeholder values which are still consistent
+    /// between runs.
+    ///
+    /// ### Arguments
+    ///
+    /// * `index`  - the index of the placeholder value to obtain. Two placeholder values generated
+    ///              from the same index are guaranteed to be equal (even across multiple test runs,
+    ///              so long as the value format doesn't change).
+    fn placeholder_indexed(index: u64) -> Self {
+        Self::placeholder_seed_parts([ index.to_le_bytes().as_slice() ])
+    }
+
+    /// Gets an array of placeholder values of this type which can be used for test purposes.
+    fn placeholder_array_seed<const N: usize>(seed: impl AsRef<[u8]>) -> [Self; N] {
+        core::array::from_fn(|n| Self::placeholder_seed_parts(
+            [ seed.as_ref(), &(n as u64).to_le_bytes() ]
+        ))
+    }
+
+    /// Gets an array of placeholder values of this type which can be used for test purposes.
+    fn placeholder_array_indexed<const N: usize>(base_index: u64) -> [Self; N] {
+        Self::placeholder_array_seed(base_index.to_le_bytes())
+    }
+}
+
+#[cfg(test)]
+impl<T: PlaceholderSeed> Placeholder for T {
+    fn placeholder() -> Self {
+        <Self as PlaceholderSeed>::placeholder_seed_parts([])
+    }
+}
+
+/// Generates the given number of pseudorandom bytes based on the given seed.
+///
+/// This is intended to be used in tests, where random but reproducible placeholder values are often
+/// required.
+///
+/// ### Arguments
+///
+/// * `seed_parts`   - the parts of the seed, which will be concatenated to form the RNG seed
+#[cfg(test)]
+pub fn placeholder_bytes<'a, const N: usize>(
+    seed_parts: impl IntoIterator<Item = &'a [u8]>
+) -> [u8; N] {
+    // Use Shake-256 to generate an arbitrarily large number of random bytes based on the given seed.
+    let mut shake256 = sha3::Shake256::default();
+    for slice in seed_parts {
+        sha3::digest::Update::update(&mut shake256, slice);
+    }
+    let mut reader = sha3::digest::ExtendableOutput::finalize_xof(shake256);
+
+    let mut res = [0u8; N];
+    sha3::digest::XofReader::read(&mut reader, &mut res);
+    res
+}