diff --git a/src/generators.rs b/src/generators.rs
index 1456741..12d7888 100644
--- a/src/generators.rs
+++ b/src/generators.rs
@@ -152,67 +152,342 @@ mod tests {
     use std::fmt::Debug;
 
     use super::*;
-    use crate::models::{FrozenGraph, Graph};
+    use crate::testing::fixtures::MakeTestGraph;
 
-    #[test]
-    fn petersen_append_graph() {
-        petersen_add::<AppendGraph>();
+    #[derive(Debug, Clone, Copy)]
+    enum Spec {
+        Path(usize),
+        Cycle(usize),
+        Complete(usize),
+        Petersen,
     }
 
-    #[test]
-    fn petersen_graph() {
-        petersen_add::<Graph>();
+    impl Spec {
+        fn generate<G: GraphTopologyAddition>(
+            &self,
+            graph: &mut G,
+        ) -> (Vec<G::Vertex>, Vec<G::Edge>) {
+            match *self {
+                Spec::Path(n) => path(graph, n),
+                Spec::Cycle(n) => cycle(graph, n),
+                Spec::Complete(n) => complete(graph, n),
+                Spec::Petersen => petersen(graph),
+            }
+        }
+
+        fn assert<G: GraphTopology>(&self, built: &Built<G>)
+        where
+            G::Vertex: Debug,
+            G::Edge: Debug,
+        {
+            match *self {
+                Spec::Path(n) => assert_path(built, n),
+                Spec::Cycle(n) => assert_cycle(built, n),
+                Spec::Complete(n) => assert_complete(built, n),
+                Spec::Petersen => assert_petersen(built),
+            }
+        }
     }
 
-    #[test]
-    fn petersen_frozen_graph() {
-        petersen_generate_as::<FrozenGraph>();
+    struct Built<G: GraphTopology> {
+        graph: G,
+        vertices: Vec<G::Vertex>,
+        edges: Vec<G::Edge>,
+        initial_vertex_count: usize,
+        initial_edge_count: usize,
     }
 
-    fn petersen_generate_as<G: GraphTopologyConversion>()
+    /// Generates the test for the `append_graph` harness for the given `Spec` expression.
+    macro_rules! min_harness_tests {
+        ($spec:expr) => {
+            #[test]
+            fn append_graph() {
+                run($spec, add_to_empty::<$crate::models::AppendGraph>);
+            }
+        };
+    }
+
+    /// Generates one test per harness for the given `Spec` expression.
+    macro_rules! all_harness_tests {
+        ($spec:expr) => {
+            min_harness_tests!($spec);
+
+            #[test]
+            fn append_graph_non_empty() {
+                run($spec, add_to_standard::<$crate::models::AppendGraph>);
+            }
+
+            #[test]
+            fn graph() {
+                run($spec, add_to_empty::<$crate::models::Graph>);
+            }
+
+            #[test]
+            fn graph_non_empty() {
+                run($spec, add_to_standard::<$crate::models::Graph>);
+            }
+
+            #[test]
+            fn frozen_graph() {
+                run($spec, conv_generate_as::<$crate::models::FrozenGraph>);
+            }
+        };
+    }
+
+    /// Generates the module tree `<group>::<case>::<harness>` for each generator case.
+    ///
+    /// The `all_harnesses` cases run on every harness, the `min_harnesses` cases only on a reduced
+    /// set of harnesses.
+    macro_rules! generator_tests {
+        ($($group:ident {
+            all { $($all_case:ident => $all_generator:expr),+ $(,)? }
+            min { $($min_case:ident => $min_generator:expr),* $(,)? }
+        })+) => {
+            $(
+                mod $group {
+                    use super::*;
+
+                    $(
+                        mod $all_case {
+                            use super::*;
+
+                            all_harness_tests!($all_generator);
+                        }
+                    )+
+
+                    $(
+                        mod $min_case {
+                            use super::*;
+
+                            min_harness_tests!($min_generator);
+                        }
+                    )*
+                }
+            )+
+        };
+    }
+
+    generator_tests! {
+        path {
+            all {
+                small => Spec::Path(4),
+            }
+            min {
+                empty => Spec::Path(0),
+                single_vertex => Spec::Path(1),
+                single_edge => Spec::Path(2),
+                large => Spec::Path(21),
+            }
+        }
+        cycle {
+            all {
+                small_even => Spec::Cycle(4),
+            }
+            min {
+                empty => Spec::Cycle(0),
+                loop_edge => Spec::Cycle(1),
+                multi_edge => Spec::Cycle(2),
+                large_odd => Spec::Cycle(21),
+            }
+        }
+        complete {
+            all {
+                small_even => Spec::Complete(4),
+            }
+            min {
+                empty => Spec::Complete(0),
+                single_vertex => Spec::Complete(1),
+                single_edge => Spec::Complete(2),
+                large_odd => Spec::Complete(13),
+            }
+        }
+    }
+
+    mod petersen {
+        use super::*;
+
+        all_harness_tests!(Spec::Petersen);
+    }
+
+    /// Builds a graph with `harness` and asserts that it matches what `spec` should produce.
+    fn run<G: GraphTopology>(spec: Spec, harness: impl FnOnce(&Spec) -> Built<G>)
     where
         G::Vertex: Debug,
         G::Edge: Debug,
     {
-        let (graph, vertices, edges) = generate_as::<G, _, _>(petersen);
-        assert_petersen(&graph, &vertices, &edges);
+        let built = harness(&spec);
+        spec.assert(&built);
     }
 
-    fn petersen_add<G: GraphTopologyAddition>()
-    where
-        G::Vertex: Debug,
-        G::Edge: Debug,
-    {
+    /// Runs `spec` on an empty graph of type `G`.
+    fn add_to_empty<G: GraphTopologyAddition>(spec: &Spec) -> Built<G> {
         let mut graph = G::default();
-        let (vertices, edges) = petersen(&mut graph);
-        assert_petersen(&graph, &vertices, &edges);
+        let (vertices, edges) = spec.generate(&mut graph);
+        Built {
+            graph,
+            vertices,
+            edges,
+            initial_vertex_count: 0,
+            initial_edge_count: 0,
+        }
     }
 
-    fn assert_petersen<G: GraphTopology>(graph: &G, vertices: &[G::Vertex], edges: &[G::Edge])
+    /// Runs `spec` on a non-empty test graph of type `G`.
+    fn add_to_standard<G: GraphTopologyAddition>(spec: &Spec) -> Built<G> {
+        let (mut graph, initial_vertices, initial_edges, _) = G::standard();
+        let (vertices, edges) = spec.generate(&mut graph);
+        Built {
+            graph,
+            vertices,
+            edges,
+            initial_vertex_count: initial_vertices.len(),
+            initial_edge_count: initial_edges.len(),
+        }
+    }
+
+    /// Runs `spec` within `generate_as` for type `G`.
+    fn conv_generate_as<G: GraphTopologyConversion>(spec: &Spec) -> Built<G> {
+        let (graph, vertices, edges) = generate_as::<G>(|graph| spec.generate(graph));
+        Built {
+            graph,
+            vertices,
+            edges,
+            initial_vertex_count: 0,
+            initial_edge_count: 0,
+        }
+    }
+
+    fn assert_path<G: GraphTopology>(built: &Built<G>, n: usize)
     where
         G::Vertex: Debug,
         G::Edge: Debug,
     {
-        assert_element_counts(graph, 10, 15);
-        assert_handles(graph.vertices(), vertices, "vertex");
-        assert_handles(graph.edges(), edges, "edge");
-        assert_no_loops_no_multi_edges(graph);
+        assert_element_counts(built, n, n.saturating_sub(1));
+        assert_handles(built.graph.vertices(), &built.vertices, "vertex");
+        assert_handles(built.graph.edges(), &built.edges, "edge");
+        assert_no_loops(built);
+        assert_no_multi_edges(built);
+        match n {
+            0 => {}
+            1 => assert_eq!(
+                built.graph.degree(built.vertices[0]),
+                0,
+                "path n == 1 should be an isolated vertex"
+            ),
+            _ => {
+                for (i, &v) in built.vertices.iter().enumerate() {
+                    assert_eq!(
+                        built.graph.degree(v),
+                        if i == 0 || i == n - 1 { 1 } else { 2 },
+                        "unexpected degree of vertex {v:?} in path n == {n}"
+                    );
+                }
+            }
+        }
+        assert_path_order(built);
+    }
+
+    fn assert_cycle<G: GraphTopology>(built: &Built<G>, n: usize)
+    where
+        G::Vertex: Debug,
+        G::Edge: Debug,
+    {
+        assert_element_counts(built, n, n);
+        assert_handles(built.graph.vertices(), &built.vertices, "vertex");
+        assert_handles(built.graph.edges(), &built.edges, "edge");
+        if n != 1 {
+            assert_no_loops(built);
+        }
+        if n != 2 {
+            assert_no_multi_edges(built);
+        }
         assert!(
-            graph.vertices().all(|v| graph.degree(v) == 3),
-            "all vertices should have degree 3"
+            built.vertices.iter().all(|&v| built.graph.degree(v) == 2),
+            "all new vertices should have degree 2"
+        );
+        assert_path_order(built);
+        // Asserts the closing edge e(n - 1) == (v(n - 1), v0).
+        if n > 0 {
+            // For n == 1, u == v and this validates the loop. For n == 2, the above asserted one of
+            // the two multi-edges, and this asserts the other.
+            let e = built.edges[n - 1];
+            let u = built.vertices[0];
+            let v = built.vertices[n - 1];
+            let incident_vertices = built.graph.incident_vertices(e);
+            assert!(
+                incident_vertices == (u, v) || incident_vertices == (v, u),
+                "edge {e:?} should have incident vertices {u:?} and {v:?}",
+            );
+        }
+    }
+
+    fn assert_complete<G: GraphTopology>(built: &Built<G>, n: usize)
+    where
+        G::Vertex: Debug,
+        G::Edge: Debug,
+    {
+        assert_element_counts(built, n, n * n.saturating_sub(1) / 2);
+        assert_handles(built.graph.vertices(), &built.vertices, "vertex");
+        assert_handles(built.graph.edges(), &built.edges, "edge");
+        // The predicate in `all` is only executed if `vertices` has any elements, i.e. for n > 0.
+        assert!(
+            built
+                .vertices
+                .iter()
+                .all(|&v| built.graph.degree(v) == n - 1),
+            "all new vertices should have degree {}",
+            n - 1
+        );
+        // Asserts that all pairs of vertices have exactly one edge between them. This also includes
+        // checks for loops and multi-edges. If there are no duplicates, then this implies that all
+        // expected edges were also matched due to the validated counts from above.
+        let mut seen = vec![false; n * n];
+        let position = |v, e| {
+            built
+                .vertices
+                .iter()
+                .position(|&x| x == v)
+                .unwrap_or_else(|| panic!("edge {e:?} has an invalid incident vertex {v:?}"))
+        };
+        for &e in &built.edges {
+            let (u, v) = built.graph.incident_vertices(e);
+            assert_ne!(u, v, "unexpected loop edge {e:?} at vertex {u:?}");
+            let (i, j) = (position(u, e), position(v, e));
+            let (i, j) = (i.min(j), i.max(j));
+            assert!(
+                !seen[i * n + j],
+                "unexpected multi-edge {e:?} between vertices {u:?} and {v:?}"
+            );
+            seen[i * n + j] = true;
+        }
+    }
+
+    fn assert_petersen<G: GraphTopology>(built: &Built<G>)
+    where
+        G::Vertex: Debug,
+        G::Edge: Debug,
+    {
+        assert_element_counts(built, 10, 15);
+        assert_handles(built.graph.vertices(), &built.vertices, "vertex");
+        assert_handles(built.graph.edges(), &built.edges, "edge");
+        assert_no_loops(built);
+        assert_no_multi_edges(built);
+        assert!(
+            built.vertices.iter().all(|&v| built.graph.degree(v) == 3),
+            "all new vertices should have degree 3"
         );
         // Checks that each pair of vertices (u, v) has no common neighbor if they are adjacent, and
         // exactly one common neighbor otherwise.
-        for (i, &v) in vertices.iter().enumerate() {
-            for &u in &vertices[i + 1..] {
-                if graph.are_adjacent(v, u) {
+        for (i, &v) in built.vertices.iter().enumerate() {
+            for &u in &built.vertices[i + 1..] {
+                if built.graph.are_adjacent(v, u) {
                     assert!(
-                        graph.common_neighbors(u, v).next().is_none(),
+                        built.graph.common_neighbors(u, v).next().is_none(),
                         "adjacent vertices {u:?} and {v:?} should not have a common neighbor"
                     );
                 } else {
                     assert_eq!(
-                        graph.common_neighbors(u, v).count(),
+                        built.graph.common_neighbors(u, v).count(),
                         1,
                         "non-adjacent vertices {u:?} and {v:?} should have exactly one common neighbor"
                     );
@@ -222,19 +497,29 @@ mod tests {
     }
 
     fn assert_element_counts<G: GraphTopology>(
-        graph: &G,
+        built: &Built<G>,
         expected_vertex_count: usize,
         expected_edge_count: usize,
     ) {
         assert_eq!(
-            graph.vertex_count(),
-            expected_vertex_count,
-            "unexpected number of vertices"
+            built.graph.vertex_count(),
+            built.initial_vertex_count + expected_vertex_count,
+            "unexpected number of added vertices"
         );
         assert_eq!(
-            graph.edge_count(),
+            built.vertices.len(),
+            expected_vertex_count,
+            "unexpected number of returned vertices"
+        );
+        assert_eq!(
+            built.graph.edge_count(),
+            built.initial_edge_count + expected_edge_count,
+            "unexpected number of added edges"
+        );
+        assert_eq!(
+            built.edges.len(),
             expected_edge_count,
-            "unexpected number of edges"
+            "unexpected number of returned edges"
         );
     }
 
@@ -253,24 +538,53 @@ mod tests {
         }
     }
 
-    fn assert_no_loops_no_multi_edges<G: GraphTopology>(graph: &G)
+    fn assert_no_loops<G: GraphTopology>(built: &Built<G>)
     where
         G::Vertex: Debug,
         G::Edge: Debug,
     {
-        for e in graph.edges() {
-            let (u, v) = graph.incident_vertices(e);
-            assert_ne!(u, v, "unexpected loop edge {e:?}");
+        for &e in &built.edges {
+            let (u, v) = built.graph.incident_vertices(e);
+            assert_ne!(u, v, "unexpected loop edge {e:?} at vertex {u:?}");
         }
-        for v in graph.vertices() {
+    }
+
+    fn assert_no_multi_edges<G: GraphTopology>(built: &Built<G>)
+    where
+        G::Vertex: Debug,
+    {
+        for &v in &built.vertices {
             let mut neighbors = Vec::new();
-            for u in graph.adjacent_vertices(v) {
-                assert!(
-                    !neighbors.contains(&u),
-                    "unexpected multi-edge between {v:?} and {u:?}"
-                );
-                neighbors.push(u);
+            let mut loop_count = 0;
+            for u in built.graph.adjacent_vertices(v) {
+                if u == v {
+                    loop_count += 1;
+                    assert!(loop_count < 3, "unexpected multi-edge loop at vertex {v:?}");
+                } else {
+                    assert!(
+                        !neighbors.contains(&u),
+                        "unexpected multi-edge between vertices {v:?} and {u:?}"
+                    );
+                    neighbors.push(u);
+                }
             }
         }
     }
+
+    /// Asserts that each returned edge *ei* connects the returned vertices *vi* and *v(i + 1)*.
+    fn assert_path_order<G: GraphTopology>(built: &Built<G>)
+    where
+        G::Vertex: Debug,
+        G::Edge: Debug,
+    {
+        for (w, &e) in built.vertices.windows(2).zip(&built.edges) {
+            let incident_vertices = built.graph.incident_vertices(e);
+            assert!(
+                incident_vertices == (w[0], w[1]) || incident_vertices == (w[1], w[0]),
+                "edge {e:?} should have incident vertices {:?} and {:?}",
+                w[0],
+                w[1]
+            );
+        }
+    }
 }