diff --git a/src/main/scala/emc/rna/RNA.scala b/src/main/scala/emc/rna/RNA.scala
index d7ed40a..07d7f73 100644
--- a/src/main/scala/emc/rna/RNA.scala
+++ b/src/main/scala/emc/rna/RNA.scala
@@ -87,7 +87,7 @@ final class RNA private(val slots: Array[Int], val length: Int)
 
     /** Returns a codon iterator for this sequence starting at given reading frame,
      * which will drop `rf` nucleotides first, RNA library writers may as conjugated
-     * with RNA application writers may prefer to read `codons` as `skip`.
+     * with RNA application writers prefer to read the `codons` reference frame as `skip`.
      *
      * @return A codon iterator for this RNA sequence.
      */
diff --git a/src/test/scala/emc/rna/RNASpecification.scala b/src/test/scala/emc/rna/RNASpecification.scala
index 33b72f5..3e6b26e 100644
--- a/src/test/scala/emc/rna/RNASpecification.scala
+++ b/src/test/scala/emc/rna/RNASpecification.scala
@@ -4,20 +4,10 @@ package rna
 import org.scalatest.funspec.*
 import org.scalatest.matchers.should.*
 
-val fixture: RNA =
-  rna"CCCCC" ++             // semi-random prefix
-  Codon.Start.asRNA ++      // [A,U,G]
-  rna"AUGCCC" ++            // semi-random post-start junk rna
-  Codon.Stop.Amber.asRNA ++ // known amber codon, also a stop codon
-  rna"CCC" ++               // semi-random junk rna
-  Codon.Stop.Opal.asRNA ++  // known opal codon, also a stop codon
-  Codon.Start.asRNA ++      // start again,...
-  rna"CAUG"                 // but include [A,U,G], after just one nucleotide
-
 class RNASpecification extends AnyFunSpec with Matchers:
 
   import Nucleotide.*
-  import AminoAcid.*
+  import RNASpecification.*
 
   describe("An RNA sequence"):
 
@@ -56,3 +46,15 @@ class RNASpecification extends AnyFunSpec with Matchers:
         Codon(A, U, G),
         Codon(C, A, U))
       )
+
+object RNASpecification:
+
+  val fixture: RNA =
+    rna"CCCCC" ++ // semi-random prefix
+      Codon.Start.asRNA ++ // [A,U,G]
+      rna"AUGCCC" ++ // semi-random post-start junk rna
+      Codon.Stop.Amber.asRNA ++ // known amber codon, also a stop codon
+      rna"CCC" ++ // semi-random junk rna
+      Codon.Stop.Opal.asRNA ++ // known opal codon, also a stop codon
+      Codon.Start.asRNA ++ // start again,...
+      rna"CAUG" // but include [A,U,G], after just one nucleotide
diff --git a/src/test/scala/emc/rna/RibosomeSpecification.scala b/src/test/scala/emc/rna/RibosomeSpecification.scala
index 7ad1271..c5d25d7 100644
--- a/src/test/scala/emc/rna/RibosomeSpecification.scala
+++ b/src/test/scala/emc/rna/RibosomeSpecification.scala
@@ -5,8 +5,8 @@ import org.scalatest.matchers.should.Matchers
 
 class RibosomeSpecification extends AnyFunSpec with Matchers:
 
-  import Nucleotide.*
   import AminoAcid.*
+  import RNASpecification.*
 
   // expected results at given reference frame
   val expected: Map[Int, Seq[Seq[AminoAcid]]] =