Fix test setup: call resetNgx() before accessing ngx global

All test setup methods were trying to access ngx.shared before the ngx
global was initialized, causing 'attempt to index global ngx (a nil value)'
errors.

Fixed by calling resetNgx() at the start of each setup() method to ensure
the ngx global exists before setting up ngx.shared and other mock properties.

tests/ddos_protection_challenge.lua

@@ -27,6 +27,9 @@ local function createMockSharedDict()
 end
 
 function TestDDoSProtectionChallenge:setup()
+    -- First reset ngx to get the base ngx object
+    resetNgx()
+
     -- Create mock shared dictionaries
     ngx.shared = {
         aproxy_bans = createMockSharedDict(),
@@ -206,6 +209,9 @@ end
 TestDDoSProtectionChallengePaths = {}
 
 function TestDDoSProtectionChallengePaths:setup()
+    -- First reset ngx to get the base ngx object
+    resetNgx()
+
     -- Create mock shared dictionaries
     ngx.shared = {
         aproxy_bans = createMockSharedDict(),
@@ -352,6 +358,9 @@ end
 TestDDoSProtectionChallengeQuestion = {}
 
 function TestDDoSProtectionChallengeQuestion:setup()
+    -- First reset ngx to get the base ngx object
+    resetNgx()
+
     ngx.shared = {
         aproxy_bans = createMockSharedDict(),
         aproxy_tokens = createMockSharedDict()
@@ -464,6 +473,9 @@ end
 TestDDoSProtectionChallengePow = {}
 
 function TestDDoSProtectionChallengePow:setup()
+    -- First reset ngx to get the base ngx object
+    resetNgx()
+
     ngx.shared = {
         aproxy_bans = createMockSharedDict(),
         aproxy_tokens = createMockSharedDict()