test: make "expect an empty body" expressible (it silently wasn't)

Execute() gated the body comparison on `test.Expected != ""`, so an empty
Expected meant "don't check the body" — which is also exactly how a ported test
has to spell PostgREST's `shouldRespondWith ""`. The two are indistinguishable,
so every ported test expecting an empty body silently degraded to a status-only
check: 116 of ~800 across insert (17), update (16), range (24), rpc (14), query
(13), embed_inner_join (15), delete (7) and others.

That is a hole in a suite whose entire purpose is catching PostgREST deviations:
it cannot see the one class of response PostgREST defines by absence — and
writes default to `Prefer: return=minimal`, so that class is every write.

Adds an explicit ExpectedEmpty bool. Additive: Go's zero value keeps every
existing test's behaviour unchanged.

Marks the three insert cases whose PostgREST comment reads `shouldRespondWith ""`
with matchStatus 201. They fail against the current POST handler — see the next
commit. The remaining 113 are left for triage: "Expected is empty" does not by
itself mean "PostgREST expects empty" (many are GETs where the porter simply
didn't fill in the body), so they need reading against their Haskell comment
rather than a bulk flip.

Author: sted

test/common.go

@@ -29,12 +29,21 @@ type Command struct {
 
 // We don't embed Command to simplify tests writing
 type Test struct {
-	Description     string
-	Method          string
-	Query           string
-	Body            string
-	Headers         Headers
-	Expected        string
+	Description string
+	Method      string
+	Query       string
+	Body        string
+	Headers     Headers
+	// Expected is the response body to compare against, JSON-normalized.
+	// An empty Expected means "no expectation" and the body is NOT checked —
+	// so it cannot express PostgREST's `shouldRespondWith ""`. Use
+	// ExpectedEmpty for that.
+	Expected string
+	// ExpectedEmpty asserts the response body is empty. Needed because many
+	// ported PostgREST tests expect exactly that (writes default to
+	// `Prefer: return=minimal`), and encoding it as `Expected: ""` silently
+	// degraded those tests to status-only checks.
+	ExpectedEmpty   bool
 	ExpectedHeaders map[string]string
 	Status          int
 }
@@ -134,6 +143,12 @@ func Execute(t *testing.T, config Config, tests []Test) {
 		body, headers, status, err := Exec(client, config, command)
 		if err != nil {
 			t.Errorf("Error: %v", err)
+		} else if test.ExpectedEmpty {
+			if len(bytes.TrimSpace(body)) != 0 {
+				t.Errorf("\n\n%d. %v\nExpected an empty body, \ngot \n\t\"%v\" \n\n(query string -> \"%v\")", i,
+					test.Description, string(body), test.Query)
+				break
+			}
 		} else if test.Expected != "" {
 			if v, ok := test.Headers["Accept"]; ok && strings.Contains(v[0], "text/csv") {
 				s1 = test.Expected

test/postgrest/insert_test.go

@@ -31,9 +31,9 @@ func TestPostgREST_Insert(t *testing.T) {
 				 		, "boolean": false, "date": "1900-01-01", "money": "$3.99"
 				 		, "enum": "foo"
 				 	}`,
-			Headers:  nil,
-			Expected: ``,
-			Status:   201,
+			Headers:       nil,
+			ExpectedEmpty: true,
+			Status:        201,
 		},
 		// 	  it "filters columns in result using &select" $
 		// 		request methodPost "/menagerie?select=integer,varchar" [("Prefer", "return=representation")]
@@ -80,9 +80,9 @@ func TestPostgREST_Insert(t *testing.T) {
 				 		 , "boolean": false, "date": "1900-01-01", "money": "$3.99"
 				 		 , "enum": "foo"
 				 	}]`,
-			Headers:  nil,
-			Expected: ``,
-			Status:   201,
+			Headers:       nil,
+			ExpectedEmpty: true,
+			Status:        201,
 		},
 		// 		request methodPost "/menagerie?select=integer,varchar"
 		// 			[("Prefer", "return=minimal")]
@@ -105,9 +105,9 @@ func TestPostgREST_Insert(t *testing.T) {
 				 		 , "boolean": false, "date": "1900-01-01", "money": "$3.99"
 				 		 , "enum": "foo"
 				 	}]`,
-			Headers:  test.Headers{"Prefer": {"return=minimal"}},
-			Expected: ``,
-			Status:   201,
+			Headers:       test.Headers{"Prefer": {"return=minimal"}},
+			ExpectedEmpty: true,
+			Status:        201,
 		},
 		// 	context "non uniform json array" $ do
 		// 	  it "rejects json array that isn't exclusivily composed of objects" $