test(wasm-plugins): lift unit-test coverage to ≥90% across 9 plugins (#3879)

Signed-off-by: jingze <daijingze.djz@alibaba-inc.com>
Co-authored-by: woody <yaodiwu618@gmail.com>

plugins/wasm-go/extensions/ext-auth/expr/expr_extra_test.go

@@ -0,0 +1,93 @@
+// Copyright (c) 2025 Alibaba Group Holding Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package expr
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// === Module A — MatchRulesDefaults ======================================
+//
+// MatchRulesDefaults is at 0% in the baseline. It is consumed by
+// config.ParseConfig as the zero-value MatchRules when the user supplies
+// no match_list, so a regression here would silently change route-skip
+// semantics from "whitelist with empty rule list" (block all by default)
+// to whatever a future zero-value happens to mean.
+
+func TestMatchRulesDefaults_WhitelistMode(t *testing.T) {
+	d := MatchRulesDefaults()
+	require.Equal(t, ModeWhitelist, d.Mode)
+}
+
+func TestMatchRulesDefaults_EmptyButNonNilRuleList(t *testing.T) {
+	d := MatchRulesDefaults()
+	require.NotNil(t, d.RuleList)
+	require.Len(t, d.RuleList, 0)
+}
+
+// In whitelist mode with an empty rule list, every (domain, method, path)
+// triple must be DENIED by the rule check (i.e. the auth server gets to see
+// the request). The dual contract — blacklist + empty rule list = ALLOW —
+// is already covered by match_rules_test.go via populated rule sets, but
+// the empty-list defaults case is an important degenerate edge.
+func TestMatchRulesDefaults_EmptyWhitelistDenies(t *testing.T) {
+	d := MatchRulesDefaults()
+	require.False(t, d.IsAllowedByMode("example.com", "GET", "/x"))
+}
+
+// === Module B — IsAllowedByMode default branch ==========================
+//
+// `default: return false` at match_rules.go:51 is unreachable through
+// MatchRulesDefaults because Mode is whitelist there. A misconfigured /
+// hand-built MatchRules with an unknown mode must safely fall back to
+// "not allowed" so the request still goes through the auth server rather
+// than silently bypassing it.
+
+func TestIsAllowedByMode_UnknownModeFallsToFalse(t *testing.T) {
+	mr := MatchRules{Mode: "not-a-mode", RuleList: []Rule{}}
+	require.False(t, mr.IsAllowedByMode("example.com", "GET", "/x"))
+}
+
+// === Module C — BuildStringMatcher edges ================================
+//
+// BuildStringMatcher is at 75%; the unknown-type error branch and the
+// invalid-regex branch are both unreached. Both must produce errors rather
+// than nil-matchers so config.parseMatchRules can surface a proper config
+// validation error.
+
+func TestBuildStringMatcher_UnknownType(t *testing.T) {
+	m, err := BuildStringMatcher("not-a-pattern", "x", false)
+	require.Error(t, err)
+	require.Nil(t, m)
+	require.Contains(t, err.Error(), "unknown string matcher type")
+}
+
+func TestBuildStringMatcher_InvalidRegex(t *testing.T) {
+	// Unbalanced "[" is a regexp.Compile error.
+	m, err := BuildStringMatcher(MatchPatternRegex, "[unbalanced", false)
+	require.Error(t, err)
+	require.Nil(t, m)
+}
+
+// IgnoreCase + already-prefixed `(?i)` regex must NOT double-prefix —
+// pins matcher.go:119-121's idempotency check.
+func TestBuildStringMatcher_RegexIgnoreCaseAlreadyPrefixed(t *testing.T) {
+	m, err := BuildStringMatcher(MatchPatternRegex, "(?i)foo", true)
+	require.NoError(t, err)
+	require.NotNil(t, m)
+	require.True(t, m.Match("FOO"))
+}