diff --git a/src/asyncresults.jl b/src/asyncresults.jl
index b2a0c5ba..5710d7bd 100644
--- a/src/asyncresults.jl
+++ b/src/asyncresults.jl
@@ -251,7 +251,8 @@ function async_execute(
     string_params = string_parameters(parameters)
     pointer_params = parameter_pointers(string_params)
 
-    async_result = _async_execute(jl_conn; binary_format=binary_format, kwargs...) do jl_conn
+    async_result =
+        _async_execute(jl_conn; binary_format=binary_format, kwargs...) do jl_conn
             GC.@preserve string_params _async_submit(
                 jl_conn, query, pointer_params; binary_format=binary_format
             )
diff --git a/test/runtests.jl b/test/runtests.jl
index 6a018f64..22f21edd 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -40,7 +40,8 @@ function count_allocs(f, args...)
     return Base.gc_alloc_count(stats.gcstats)
 end
 
-@testset "LibPQ" begin
+usenonblocking = get(ENV, "usenonblocking", false)
+@testset "LibPQ $(usenonblocking ? "(nonblocking connection)" : "")" begin
 
 @testset "ConninfoDisplay" begin
     @test parse(LibPQ.ConninfoDisplay, "") == LibPQ.Normal
@@ -82,6 +83,7 @@ end
 
     @testset "Example SELECT" begin
         conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=false)
+        LibPQ.setnonblocking(conn, nonblock=usenonblocking)
         @test conn isa LibPQ.Connection
         @test isopen(conn)
         @test status(conn) == LibPQ.libpq_c.CONNECTION_OK
@@ -190,6 +192,7 @@ end
 
     @testset "Example INSERT and DELETE" begin
         conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+        LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
         result = execute(conn, """
             CREATE TEMPORARY TABLE libpqjl_test (
@@ -333,6 +336,7 @@ end
     @testset "load!" begin
         @testset "issue #204" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             close(execute(conn, """
                 CREATE TEMPORARY TABLE libpqjl_test (
@@ -357,6 +361,7 @@ end
     @testset "COPY FROM" begin
         @testset "Example COPY FROM" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, """
                 CREATE TEMPORARY TABLE libpqjl_test (
@@ -401,6 +406,7 @@ end
 
         @testset "Wrong column order" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, """
                 CREATE TEMPORARY TABLE libpqjl_test (
@@ -458,6 +464,7 @@ end
             local saved_conn
 
             was_open = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true) do jl_conn
+                LibPQ.setnonblocking(jl_conn, nonblock=usenonblocking)
                 saved_conn = jl_conn
                 return isopen(jl_conn)
             end
@@ -466,6 +473,7 @@ end
             @test !isopen(saved_conn)
 
             @test_throws LibPQ.Errors.PQConnectionError LibPQ.Connection("dbname=123fake user=$DATABASE_USER"; throw_error=true) do jl_conn
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
                 saved_conn = jl_conn
                 @test false
             end
@@ -475,6 +483,7 @@ end
 
         @testset "Version Numbers" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             # update this test before PostgreSQL 20.0 ;)
             @test LibPQ.pqv"7" <= LibPQ.server_version(conn) <= LibPQ.pqv"20"
@@ -482,6 +491,7 @@ end
 
         @testset "Encoding" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             @test LibPQ.encoding(conn) == "UTF8"
 
@@ -513,6 +523,7 @@ end
                 throw_error=true,
                 type_map=Dict(:interval => String),
             )
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             conn_info = LibPQ.conninfo(conn)
             options = first(filter(conn_info) do conn_opt
@@ -632,6 +643,8 @@ end
         @testset "Finalizer" begin
             closed_flags = map(1:50) do _
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
+
                 closed = conn.closed
                 finalize(conn)
                 return closed
@@ -646,6 +659,8 @@ end
 
             closed_flags = map(1:50) do _
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
+
                 push!(results, execute(conn, "SELECT 1;"))
                 return conn.closed
             end
@@ -661,6 +676,8 @@ end
             # with AsyncResults, which hold a reference to Connection
             closed_flags = asyncmap(1:50) do _
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
+
                 wait(async_execute(conn, "SELECT pg_sleep(1);"))
                 return conn.closed
             end
@@ -707,6 +724,8 @@ end
 
             @testset "throw_error=false" begin
                 conn = LibPQ.Connection("dbname=123fake user=$DATABASE_USER"; throw_error=false)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
+
                 @test conn isa LibPQ.Connection
                 @test status(conn) == LibPQ.libpq_c.CONNECTION_BAD
                 @test isopen(conn)
@@ -725,6 +744,8 @@ end
                 @test_throws LibPQ.Errors.PQConnectionError LibPQ.Connection("dbname=123fake user=$DATABASE_USER"; throw_error=true)
 
                 conn = LibPQ.Connection("dbname=123fake user=$DATABASE_USER"; throw_error=false)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
+
                 @test conn isa LibPQ.Connection
                 @test status(conn) == LibPQ.libpq_c.CONNECTION_BAD
                 @test isopen(conn)
@@ -740,6 +761,7 @@ end
     @testset "Results" begin
         @testset "Nulls" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, "SELECT NULL"; throw_error=true)
             @test status(result) == LibPQ.libpq_c.PGRES_TUPLES_OK
@@ -824,6 +846,7 @@ end
 
         @testset "Not Nulls" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, "SELECT NULL"; not_null=[false], throw_error=true)
             @test status(result) == LibPQ.libpq_c.PGRES_TUPLES_OK
@@ -949,6 +972,7 @@ end
 
         @testset "Tables.jl" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, """
                 SELECT no_nulls, yes_nulls FROM (
@@ -991,6 +1015,7 @@ end
 
         @testset "Duplicate names" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, "SELECT 1 AS col, 2 AS col;", not_null=true, throw_error=true)
             columns = Tables.columns(result)
@@ -1007,6 +1032,7 @@ end
 
         @testset "Uppercase Columns" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(conn, "SELECT 1 AS \"Column\";")
             @test num_columns(result) == 1
@@ -1025,6 +1051,7 @@ end
 
         @testset "PQResultError" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             try
                 execute(conn, "SELECT log(-1);")
@@ -1072,6 +1099,7 @@ end
         @testset "Type Conversions" begin
             @testset "Deprecations" begin
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                 result = execute(conn, "SELECT 'infinity'::timestamp;")
 
@@ -1089,6 +1117,7 @@ end
 
             @testset "Automatic" begin
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                 result = execute(conn, """
                     SELECT oid, typname, typlen, typbyval, typcategory
@@ -1120,6 +1149,7 @@ end
 
             @testset "Overrides" begin
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                 result = execute(conn, "SELECT 4::bigint;")
                 @test first(first(result)) === Int64(4)
@@ -1169,6 +1199,7 @@ end
                 @testset for binary_format in (LibPQ.TEXT, LibPQ.BINARY)
                     @testset "Default Types" begin
                         conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                        LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                         test_data = [
                             ("3", Cint(3)),
@@ -1335,6 +1366,7 @@ end
 
                     @testset "Specified Types" begin
                         conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                        LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                         test_data = [
                             ("3", UInt, UInt(3)),
@@ -1428,6 +1460,7 @@ end
 
         @testset "Parameters" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             @testset "Arrays" begin
                 tests = (
@@ -1542,6 +1575,7 @@ end
 
         @testset "SQLString" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             execute(conn, sql```
                CREATE TEMPORARY TABLE libpq_test_users (
@@ -1577,6 +1611,7 @@ end
         @testset "Query Errors" begin
             @testset "Syntax Errors" begin
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                 result = execute(conn, "SELORCT NUUL;"; throw_error=false)
                 @test status(result) == LibPQ.libpq_c.PGRES_FATAL_ERROR
@@ -1595,6 +1630,7 @@ end
 
             @testset "Wrong No. Parameters" begin
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                 result = execute(conn, "SELORCT \$1;", String[]; throw_error=false)
                 @test status(result) == LibPQ.libpq_c.PGRES_FATAL_ERROR
@@ -1619,6 +1655,7 @@ end
 
         @testset "Interface Errors" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = execute(
                 conn,
@@ -1652,6 +1689,7 @@ end
 
                 # Establish connection and construct temporary table.
                 conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER")
+                LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
                 # Get the column.
                 result = execute(
@@ -1678,6 +1716,7 @@ end
     @testset "Statements" begin
         @testset "No Params, Output" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             stmt = prepare(conn, "SELECT oid, typname FROM pg_type")
 
@@ -1699,6 +1738,7 @@ end
 
         @testset "Params, Output" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             stmt = prepare(conn, "SELECT oid, typname FROM pg_type WHERE oid = \$1")
 
@@ -1723,11 +1763,13 @@ end
         end
     end
 
-    @testset "AsyncResults" begin
+    @testset "AsyncResults (usenonblocking connection=$usenonblocking)" for usenonblocking in [true, false]
+        @info "usenonblocking" usenonblocking
         trywait(ar::LibPQ.AsyncResult) = (try wait(ar) catch end; nothing)
 
         @testset "Basic" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             ar = async_execute(conn, "SELECT pg_sleep(2);"; throw_error=false)
             yield()
@@ -1750,6 +1792,7 @@ end
 
         @testset "Parameters" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             ar = async_execute(
                 conn,
@@ -1782,6 +1825,7 @@ end
         # Ensures queries wait for previous query completion before starting
         @testset "Wait in line to complete" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             first_ar = async_execute(conn, "SELECT pg_sleep(4);")
             yield()
@@ -1811,6 +1855,7 @@ end
 
         @testset "Cancel" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             # final query needs to be one that actually does something
             # on Windows, first query also needs to do something
@@ -1843,6 +1888,7 @@ end
 
         @testset "Canceled by closing connection" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             # final query needs to be one that actually does something
             # on Windows, first query also needs to do something
@@ -1875,6 +1921,7 @@ end
 
         @testset "FDWatcher: bad file descriptor (EBADF)" begin
             conn = LibPQ.Connection("dbname=postgres user=$DATABASE_USER"; throw_error=true)
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             ar = async_execute(conn, "SELECT pg_sleep(3); SELECT * FROM pg_type;")
             yield()
@@ -1898,6 +1945,7 @@ end
         @testset "DBInterface integration" begin
             conn = DBInterface.connect(LibPQ.Connection, "dbname=postgres user=$DATABASE_USER")
             @test conn isa LibPQ.Connection
+            LibPQ.setnonblocking(conn, nonblock=usenonblocking)
 
             result = DBInterface.execute(
                 conn,