init: archlens — architecture diagram generator

Hex arch + DDD, tree-sitter parsing, Mermaid/ASCII output.
Supports Rust + Python. 92 tests. CI, diff, --check for staleness detection.

crates/application/tests/render_diagrams_tests.rs

@@ -0,0 +1,78 @@
+mod fakes;
+
+use archlens_application::queries::RenderDiagrams;
+use archlens_domain::{
+    CodeElement, CodeElementKind, CodeGraph, FilePath, ModuleName, OutputConfig,
+};
+
+use fakes::{FakeDiagramRenderer, FakeOutputWriter};
+
+fn build_graph() -> CodeGraph {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/service.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "BillingService",
+            CodeElementKind::Class,
+            FilePath::new("src/billing.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Billing").unwrap()),
+    );
+    graph
+}
+
+#[test]
+fn renders_single_diagram_and_writes_output() {
+    let renderer = FakeDiagramRenderer::new();
+    let writer = FakeOutputWriter::new();
+    let config = OutputConfig::default();
+
+    let use_case = RenderDiagrams::new(renderer, writer);
+    use_case.execute(&build_graph(), &config).unwrap();
+
+    let outputs = use_case.writer().written_outputs();
+    assert_eq!(outputs.len(), 1);
+    assert_eq!(outputs[0].files().len(), 1);
+}
+
+#[test]
+fn split_mode_renders_overview_plus_per_module_diagrams() {
+    let renderer = FakeDiagramRenderer::new();
+    let writer = FakeOutputWriter::new();
+    let config = OutputConfig::default().with_split_by_module(true);
+
+    let graph = build_graph(); // has 2 modules: Orders, Billing
+
+    let use_case = RenderDiagrams::new(renderer, writer);
+    use_case.execute(&graph, &config).unwrap();
+
+    let outputs = use_case.writer().written_outputs();
+    // 1 overview + 2 module diagrams = 3 writes
+    assert_eq!(outputs.len(), 3);
+}
+
+#[test]
+fn empty_graph_still_produces_output() {
+    let renderer = FakeDiagramRenderer::new();
+    let writer = FakeOutputWriter::new();
+    let config = OutputConfig::default();
+
+    let graph = CodeGraph::new();
+
+    let use_case = RenderDiagrams::new(renderer, writer);
+    use_case.execute(&graph, &config).unwrap();
+
+    let outputs = use_case.writer().written_outputs();
+    assert_eq!(outputs.len(), 1);
+}