tests: expand negative SSE and table-driven coverage; add docs/testing.md; use shared fixtures

4 files changed, 72 insertions, 2 deletions

diff --git a/REPORT.md b/REPORT.md
index 37ab643..7da6b27 100644
--- a/REPORT.md
+++ b/REPORT.md
@@ -77,7 +77,7 @@ Legend: [ ] pending · [~] in progress · [x] done/partially done
 - [x] Expand Copilot mocked responses: multi-choice, error object in body; assert parsing and error propagation.
 
 6) General
-- [x] Convert repetitive tests to table-driven style where appropriate (e.g., completion prefix/strip; instruction markers; label/filter).
+- [x] Convert repetitive tests to table-driven style where appropriate (e.g., completion prefix/strip; instruction markers; label/filter; code fences/inline spans).
 - [ ] Introduce a shared set of realistic mock responses (multi-line code, markdown, malformed json) and reuse across tests.
 
 ## Progress (latest)
@@ -103,7 +103,7 @@ Legend: [ ] pending · [~] in progress · [x] done/partially done
 - [x] 3) lsp e2e chat/document: chat test now uses multi-line reply and validates insertion contains both lines; document resolve uses multi-line docblock.
 - [x] 4) lsp completion: manual-invoke test now uses a multi-line realistic function signature with body; still passes and exercises formatting.
 - [x] 5) llm providers: added OpenAI success + SSE stream and Copilot token+chat + Codex SSE tests; coverage ≥80%. Expanded with multi-choice and error-body cases.
-- [x] 6) General: introduced shared fixtures (internal/testutil) and added table-driven tests for code fences, inline spans, label selection, prefix stripping, and instruction markers.
+- [x] 6) General: introduced shared fixtures (internal/testutil) and added table-driven tests for code fences, inline spans, label selection, prefix stripping, and instruction markers. Documented patterns in docs/testing.md.
 - [x]    Added table-driven tests for instruction marker extraction and prefix stripping.
 
 ## Next actions (prioritized)
diff --git a/docs/testing.md b/docs/testing.md
new file mode 100644
index 0000000..eff6f2e
--- /dev/null
+++ b/docs/testing.md
@@ -0,0 +1,16 @@
+# Testing Guide
+
+This repository includes a growing test suite designed to be realistic and robust.
+
+Key patterns:
+
+- Table‑driven tests: consolidate repetitive scenarios into concise tables (see `internal/lsp/*_table_test.go`).
+- Shared fixtures: use `internal/testutil/fixtures.go` for multi‑line docblocks, chat replies, function suggestions, and markdown fences.
+- Provider mocks: use `httptest.Server` and/or custom `http.RoundTripper` to simulate OpenAI/Copilot/Ollama responses, including success, stream (SSE), and error cases.
+- E2E LSP tests: capture JSON‑RPC frames from the in‑memory server (`captureResponse`, `captureRequest`) and validate code actions, resolves, and chat edits.
+
+Suggested additions:
+
+- Expand table‑driven coverage for completion edit computations and label/filter selection.
+- Add more negative tests (malformed SSE/JSON payloads) to assert robust error handling.
+
diff --git a/internal/llm/copilot_http_test.go b/internal/llm/copilot_http_test.go
index 4c2b7fe..30144d1 100644
--- a/internal/llm/copilot_http_test.go
+++ b/internal/llm/copilot_http_test.go
@@ -108,6 +108,46 @@ func TestCopilot_Chat_MultiChoice_And_ErrorBody(t *testing.T) {
     }
 }
 
+func TestCopilot_CodeCompletion_MalformedAndEmpty(t *testing.T) {
+    c := newCopilot("https://api.githubcopilot.com", "gpt-4o-mini", "API", f64p(0.1)).(copilotClient)
+    tr := rtFunc2(func(r *http.Request) (*http.Response, error) {
+        if r.URL.Host == "api.github.com" && r.URL.Path == "/copilot_internal/v2/token" {
+            rw := httptest.NewRecorder(); _ = json.NewEncoder(rw).Encode(map[string]string{"token":"tok"}); res := rw.Result(); res.StatusCode = 200; return res, nil
+        }
+        if r.URL.Host == "copilot-proxy.githubusercontent.com" && strings.HasSuffix(r.URL.Path, "/v1/engines/copilot-codex/completions") {
+            rw := httptest.NewRecorder()
+            // malformed line
+            rw.WriteString("data: {bad}\n")
+            // done; should produce empty suggestions
+            rw.WriteString("data: [DONE]\n")
+            res := rw.Result(); res.StatusCode = 200; return res, nil
+        }
+        return http.DefaultTransport.RoundTrip(r)
+    })
+    c.httpClient = &http.Client{Transport: tr, Timeout: 5 * time.Second}
+    out, err := c.CodeCompletion(context.Background(), "p", "s", 1, "go", 0.1)
+    if err != nil { t.Fatalf("unexpected error: %v", err) }
+    if len(out) != 0 { t.Fatalf("expected empty suggestions, got %#v", out) }
+
+    // Now include one good chunk after malformed
+    tr2 := rtFunc2(func(r *http.Request) (*http.Response, error) {
+        if r.URL.Host == "api.github.com" && r.URL.Path == "/copilot_internal/v2/token" {
+            rw := httptest.NewRecorder(); _ = json.NewEncoder(rw).Encode(map[string]string{"token":"tok"}); res := rw.Result(); res.StatusCode = 200; return res, nil
+        }
+        if r.URL.Host == "copilot-proxy.githubusercontent.com" && strings.HasSuffix(r.URL.Path, "/v1/engines/copilot-codex/completions") {
+            rw := httptest.NewRecorder()
+            rw.WriteString("data: {bad}\n")
+            rw.WriteString("data: {\"choices\":[{\"index\":0,\"text\":\"OK\"}]}\n")
+            rw.WriteString("data: [DONE]\n")
+            res := rw.Result(); res.StatusCode = 200; return res, nil
+        }
+        return http.DefaultTransport.RoundTrip(r)
+    })
+    c.httpClient = &http.Client{Transport: tr2, Timeout: 5 * time.Second}
+    out2, err := c.CodeCompletion(context.Background(), "p", "s", 1, "go", 0.1)
+    if err != nil || len(out2) != 1 || out2[0] != "OK" { t.Fatalf("unexpected: %v %#v", err, out2) }
+}
+
 func TestParseJWTExp_AndParseInt64(t *testing.T) {
     // Valid base64 payload
     payload := `{"exp": 1700000000}`
diff --git a/internal/llm/openai_http_test.go b/internal/llm/openai_http_test.go
index 78830ba..45f0c99 100644
--- a/internal/llm/openai_http_test.go
+++ b/internal/llm/openai_http_test.go
@@ -63,6 +63,20 @@ func TestOpenAI_ChatStream_SSE_ErrorChunk(t *testing.T) {
     }
 }
 
+func TestOpenAI_Chat_DecodeError_StatusOK(t *testing.T) {
+    // Return status 200 but invalid JSON body; Chat should return an error
+    srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+        w.WriteHeader(200)
+        io.WriteString(w, "{invalid")
+    }))
+    defer srv.Close()
+    c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+    c.httpClient = srv.Client()
+    if _, err := c.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}}); err == nil {
+        t.Fatalf("expected decode error for invalid JSON body")
+    }
+}
+
 func TestOpenAI_Chat_MultiChoiceAndErrorBody(t *testing.T) {
     // Multi-choice success: return two choices with different finish reasons
     srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {