diff --git a/Compiler/src/ssair/verify.jl b/Compiler/src/ssair/verify.jl
index 14ca6ef2dbe9a3..59051058e1750c 100644
--- a/Compiler/src/ssair/verify.jl
+++ b/Compiler/src/ssair/verify.jl
@@ -104,7 +104,7 @@ function verify_ir(ir::IRCode, print::Bool=true,
         error_args = Any["IR verification failed."]
         if isdefined(Core, :Main) && isdefined(Core.Main, :Base)
             # ensure we use I/O that does not yield, as this gets called during compilation
-            firstline = invokelatest(Core.Main.Base.IRShow.debuginfo_firstline, ir.debuginfo)
+            firstline = invokelatest(IRShow.debuginfo_firstline, ir.debuginfo)
         else
             firstline = nothing
         end
diff --git a/Compiler/test/AbstractInterpreter.jl b/Compiler/test/AbstractInterpreter.jl
index 81659443038e49..df0dad79c156f2 100644
--- a/Compiler/test/AbstractInterpreter.jl
+++ b/Compiler/test/AbstractInterpreter.jl
@@ -1,14 +1,8 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-using Test
+module test_AbstractInterpreter
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+using Test
 
 include("irutils.jl")
 include("newinterp.jl")
@@ -542,3 +536,5 @@ let interp = DebugInterp()
     end
     @test found
 end
+
+end # module test_AbstractInterpreter
diff --git a/Compiler/test/EAUtils.jl b/Compiler/test/EAUtils.jl
index cec33ca265a803..5a5c42fc891060 100644
--- a/Compiler/test/EAUtils.jl
+++ b/Compiler/test/EAUtils.jl
@@ -2,13 +2,7 @@ module EAUtils
 
 export code_escapes, @code_escapes, __clear_cache!
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+include("setup_Compiler.jl")
 
 using ..EscapeAnalysis
 const EA = EscapeAnalysis
@@ -267,22 +261,22 @@ end
 
 function print_with_info(preprint, postprint, io::IO, ir::IRCode, source::Bool)
     io = IOContext(io, :displaysize=>displaysize(io))
-    used = Base.IRShow.stmts_used(io, ir)
+    used = Compiler.IRShow.stmts_used(io, ir)
     if source
         line_info_preprinter = function (io::IO, indent::String, idx::Int)
-            r = Base.IRShow.inline_linfo_printer(ir)(io, indent, idx)
+            r = Compiler.IRShow.inline_linfo_printer(ir)(io, indent, idx)
             idx ≠ 0 && preprint(io, idx)
             return r
         end
     else
-        line_info_preprinter = Base.IRShow.lineinfo_disabled
+        line_info_preprinter = Compiler.IRShow.lineinfo_disabled
     end
-    line_info_postprinter = Base.IRShow.default_expr_type_printer
+    line_info_postprinter = Compiler.IRShow.default_expr_type_printer
     preprint(io)
     bb_idx_prev = bb_idx = 1
     for idx = 1:length(ir.stmts)
         preprint(io, idx)
-        bb_idx = Base.IRShow.show_ir_stmt(io, ir, idx, line_info_preprinter, line_info_postprinter, ir.sptypes, used, ir.cfg, bb_idx)
+        bb_idx = Compiler.IRShow.show_ir_stmt(io, ir, idx, line_info_preprinter, line_info_postprinter, ir.sptypes, used, ir.cfg, bb_idx)
         postprint(io, idx, bb_idx != bb_idx_prev)
         bb_idx_prev = bb_idx
     end
diff --git a/Compiler/test/codegen.jl b/Compiler/test/codegen.jl
index 90ec16ca3b7ac1..0e425a8d553b47 100644
--- a/Compiler/test/codegen.jl
+++ b/Compiler/test/codegen.jl
@@ -2,17 +2,14 @@
 
 # tests for codegen and optimizations
 
+module test_codegen
+
 using Random
 using InteractiveUtils
 using Libdl
+using Test
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+include("setup_Compiler.jl")
 
 const opt_level = Base.JLOptions().opt_level
 const coverage = (Base.JLOptions().code_coverage > 0) || (Base.JLOptions().malloc_log > 0)
@@ -1032,3 +1029,5 @@ for a in ((@noinline Ref{Int}(2)),
         @test ex === a
     end
 end
+
+end # test_codegen
diff --git a/Compiler/test/compact.jl b/Compiler/test/compact.jl
index a636ab8172d63f..4aa8532c4cca72 100644
--- a/Compiler/test/compact.jl
+++ b/Compiler/test/compact.jl
@@ -1,10 +1,10 @@
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+# This file is a part of Julia. License is MIT: https://julialang.org/license
+
+module test_compact
+
+using Test
+
+include("irutils.jl")
 
 using .Compiler: IncrementalCompact, insert_node_here!, finish,
     NewInstruction, verify_ir, ReturnNode, SSAValue
@@ -57,3 +57,5 @@ end
     verify_ir(new_ir)
     @test length(new_ir.cfg.blocks) == 1
 end
+
+end # module test_compact
diff --git a/Compiler/test/contextual.jl b/Compiler/test/contextual.jl
index 08dc68ba42b34c..a162f3367f9e37 100644
--- a/Compiler/test/contextual.jl
+++ b/Compiler/test/contextual.jl
@@ -1,15 +1,10 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_contextual
+
 # N.B.: This file is also run from interpreter.jl, so needs to be standalone-executable
 using Test
-
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+include("setup_Compiler.jl")
 
 # Cassette
 # ========
@@ -131,3 +126,5 @@ f() = 2
 foo(i) = i+bar(Val(1))
 
 @test @inferred(overdub(Ctx(), foo, 1)) == 43
+
+end # module test_contextual
diff --git a/Compiler/test/datastructures.jl b/Compiler/test/datastructures.jl
index 6b37d7c89e684d..608e4e770998a3 100644
--- a/Compiler/test/datastructures.jl
+++ b/Compiler/test/datastructures.jl
@@ -1,12 +1,6 @@
-using Test
+# This file is a part of Julia. License is MIT: https://julialang.org/license
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+include("setup_Compiler.jl")
 
 @testset "CachedMethodTable" begin
     # cache result should be separated per `limit` and `sig`
diff --git a/Compiler/test/effects.jl b/Compiler/test/effects.jl
index e4677daf0c483d..d4647f81d19117 100644
--- a/Compiler/test/effects.jl
+++ b/Compiler/test/effects.jl
@@ -1,3 +1,5 @@
+module test_effects
+
 using Test
 include("irutils.jl")
 
@@ -1382,3 +1384,5 @@ end |> Compiler.is_nothrow
 @test Base.infer_effects() do
     @ccall unsafecall()::Cvoid
 end == Compiler.EFFECTS_UNKNOWN
+
+end # module test_effects
diff --git a/Compiler/test/inference.jl b/Compiler/test/inference.jl
index 26fc80470795f2..7c45504a6717f0 100644
--- a/Compiler/test/inference.jl
+++ b/Compiler/test/inference.jl
@@ -1,9 +1,13 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_inference
+
+using Test
+
 include("irutils.jl")
 
 # tests for Compiler correctness and precision
-import .Compiler: Const, Conditional, ⊑, ReturnNode, GotoIfNot
+using .Compiler: Conditional, ⊑
 isdispatchelem(@nospecialize x) = !isa(x, Type) || Compiler.isdispatchelem(x)
 
 using Random, Core.IR
@@ -823,7 +827,7 @@ end
 
 # Issue 19641
 foo19641() = let a = 1.0
-    Compiler.return_type(x -> x + a, Tuple{Float64})
+    Base.Compiler.return_type(x -> x + a, Tuple{Float64})
 end
 @inferred foo19641()
 
@@ -977,15 +981,15 @@ test_no_apply(::Any) = true
 
 # issue #20033
 # check return_type_tfunc for calls where no method matches
-bcast_eltype_20033(f, A) = Compiler.return_type(f, Tuple{eltype(A)})
+bcast_eltype_20033(f, A) = Base.Compiler.return_type(f, Tuple{eltype(A)})
 err20033(x::Float64...) = prod(x)
 @test bcast_eltype_20033(err20033, [1]) === Union{}
 @test Base.return_types(bcast_eltype_20033, (typeof(err20033), Vector{Int},)) == Any[Type{Union{}}]
 # return_type on builtins
-@test Compiler.return_type(tuple, Tuple{Int,Int8,Int}) === Tuple{Int,Int8,Int}
+@test Base.Compiler.return_type(tuple, Tuple{Int,Int8,Int}) === Tuple{Int,Int8,Int}
 
 # issue #21088
-@test Compiler.return_type(typeof, Tuple{Int}) == Type{Int}
+@test Base.Compiler.return_type(typeof, Tuple{Int}) == Type{Int}
 
 # Inference of constant svecs
 @eval fsvecinf() = $(QuoteNode(Core.svec(Tuple{Int,Int}, Int)))[1]
@@ -1535,7 +1539,7 @@ let nfields_tfunc(@nospecialize xs...) =
     @test sizeof_nothrow(String)
     @test !sizeof_nothrow(Type{String})
     @test sizeof_tfunc(Type{Union{Int64, Int32}}) == Const(Core.sizeof(Union{Int64, Int32}))
-    let PT = Core.PartialStruct(Base.Compiler.fallback_lattice, Tuple{Int64,UInt64}, Any[Const(10), UInt64])
+    let PT = Core.PartialStruct(Compiler.fallback_lattice, Tuple{Int64,UInt64}, Any[Const(10), UInt64])
         @test sizeof_tfunc(PT) === Const(16)
         @test nfields_tfunc(PT) === Const(2)
         @test sizeof_nothrow(PT)
@@ -1721,7 +1725,7 @@ g_test_constant() = (f_constant(3) == 3 && f_constant(4) == 4 ? true : "BAD")
 f_pure_add() = (1 + 1 == 2) ? true : "FAIL"
 @test @inferred f_pure_add()
 
-import Core: Const
+using Core: Const
 mutable struct ARef{T}
     @atomic x::T
 end
@@ -1762,7 +1766,7 @@ let getfield_tfunc(@nospecialize xs...) =
     @test getfield_tfunc(ARef{Int},Const(:x),Bool,Bool) === Union{}
 end
 
-import .Compiler: Const
+using Core: Const
 mutable struct XY{X,Y}
     x::X
     y::Y
@@ -2235,7 +2239,7 @@ end
     end |> only == Int
     # the `fargs = nothing` edge case
     @test Base.return_types((Any,)) do a
-        Compiler.return_type(invoke, Tuple{typeof(ispositive), Type{Tuple{Any}}, Any})
+        Base.Compiler.return_type(invoke, Tuple{typeof(ispositive), Type{Tuple{Any}}, Any})
     end |> only == Type{Bool}
 
     # `InterConditional` handling: `abstract_call_opaque_closure`
@@ -2765,8 +2769,6 @@ end |> only === Int
 
 # `apply_type_tfunc` accuracy for constrained type construction
 # https://github.com/JuliaLang/julia/issues/47089
-import Core: Const
-import .Compiler: apply_type_tfunc
 struct Issue47089{A<:Number,B<:Number} end
 let 𝕃 = Compiler.fallback_lattice
     A = Type{<:Integer}
@@ -3324,8 +3326,8 @@ _rttf_test(::Int16) = 0
 _rttf_test(::Int32) = 0
 _rttf_test(::Int64) = 0
 _rttf_test(::Int128) = 0
-_call_rttf_test() = Compiler.return_type(_rttf_test, Tuple{Any})
-@test Compiler.return_type(_rttf_test, Tuple{Any}) === Int
+_call_rttf_test() = Base.Compiler.return_type(_rttf_test, Tuple{Any})
+@test Base.Compiler.return_type(_rttf_test, Tuple{Any}) === Int
 @test _call_rttf_test() === Int
 
 f_with_Type_arg(::Type{T}) where {T} = T
@@ -3379,9 +3381,9 @@ struct FooPartial
     b::Int
     c::Int
 end
-let PT1 = PartialStruct(Base.Compiler.fallback_lattice, FooPartial, Any[Const(1), Const(2), Int]),
-    PT2 = PartialStruct(Base.Compiler.fallback_lattice, FooPartial, Any[Const(1), Int, Int]),
-    PT3 = PartialStruct(Base.Compiler.fallback_lattice, FooPartial, Any[Const(1), Int, Const(3)])
+let PT1 = PartialStruct(Compiler.fallback_lattice, FooPartial, Any[Const(1), Const(2), Int]),
+    PT2 = PartialStruct(Compiler.fallback_lattice, FooPartial, Any[Const(1), Int, Int]),
+    PT3 = PartialStruct(Compiler.fallback_lattice, FooPartial, Any[Const(1), Int, Const(3)])
 
     @test PT1 ⊑ PT2
     @test !(PT1 ⊑ PT3) && !(PT2 ⊑ PT1)
@@ -4554,7 +4556,8 @@ end |> only == Tuple{Int,Int}
 end |> only == Int
 
 # form PartialStruct for mutables with `const` field
-import .Compiler: Const, ⊑
+using Core: Const
+using .Compiler: ⊑
 mutable struct PartialMutable{S,T}
     const s::S
     t::T
@@ -4787,7 +4790,7 @@ end
 # at top level.
 @test let
     Base.Experimental.@force_compile
-    Compiler.return_type(+, NTuple{2, Rational})
+    Base.Compiler.return_type(+, NTuple{2, Rational})
 end == Rational
 
 # vararg-tuple comparison within `Compiler.PartialStruct`
@@ -5185,9 +5188,9 @@ end |> only === Tuple{Int,Symbol}
     end
 end) == Type{Nothing}
 
-# Test that Compiler.return_type inference works for the 1-arg version
+# Test that Base.Compiler.return_type inference works for the 1-arg version
 @test Base.return_types() do
-    Compiler.return_type(Tuple{typeof(+), Int, Int})
+    Base.Compiler.return_type(Tuple{typeof(+), Int, Int})
 end |> only == Type{Int}
 
 # Test that NamedTuple abstract iteration works for PartialStruct/Const
@@ -5723,7 +5726,7 @@ end
 @eval function has_tuin()
     $(Expr(:throw_undef_if_not, :x, false))
 end
-@test Compiler.return_type(has_tuin, Tuple{}) === Union{}
+@test Base.infer_return_type(has_tuin, Tuple{}) === Union{}
 @test_throws UndefVarError has_tuin()
 
 function gen_tuin_from_arg(world::UInt, source, _, _)
@@ -5778,7 +5781,7 @@ end
 
 # We want to make sure that both this returns `Tuple` and that
 # it doesn't infinite loop inside inference.
-@test Compiler.return_type(gen_infinite_loop_ssa, Tuple{}) === Tuple
+@test Base.infer_return_type(gen_infinite_loop_ssa, Tuple{}) === Tuple
 
 # inference local cache lookup with extended lattice elements that may be transformed
 # by `matching_cache_argtypes`
@@ -5814,7 +5817,7 @@ function foo54341(a, b, c, d, args...)
 end
 bar54341(args...) = foo54341(4, args...)
 
-@test Compiler.return_type(bar54341, Tuple{Vararg{Int}}) === Int
+@test Base.infer_return_type(bar54341, Tuple{Vararg{Int}}) === Int
 
 # `PartialStruct` for partially initialized structs:
 struct PartiallyInitialized1
@@ -5951,7 +5954,7 @@ end
 # InterConditional rt with Vararg argtypes
 fcondvarargs(a, b, c, d) = isa(d, Int64)
 gcondvarargs(a, x...) = return fcondvarargs(a, x...) ? isa(a, Int64) : !isa(a, Int64)
-@test Compiler.return_type(gcondvarargs, Tuple{Vararg{Any}}) === Bool
+@test Base.infer_return_type(gcondvarargs, Tuple{Vararg{Any}}) === Bool
 
 # JuliaLang/julia#55627: argtypes check in `abstract_call_opaque_closure`
 issue55627_make_oc() = Base.Experimental.@opaque (x::Int) -> 2x
@@ -6098,4 +6101,6 @@ function func_swapglobal!_must_throw(x)
     swapglobal!(@__MODULE__, :swapglobal!_must_throw, x)
 end
 @test Base.infer_return_type(func_swapglobal!_must_throw, (Int,); interp=SwapGlobalInterp()) === Union{}
-@test !Base.Compiler.is_effect_free(Base.infer_effects(func_swapglobal!_must_throw, (Int,); interp=SwapGlobalInterp()) )
+@test !Compiler.is_effect_free(Base.infer_effects(func_swapglobal!_must_throw, (Int,); interp=SwapGlobalInterp()) )
+
+end # test_inference
diff --git a/Compiler/test/inline.jl b/Compiler/test/inline.jl
index 158d9f545220a2..75c36429a39b41 100644
--- a/Compiler/test/inline.jl
+++ b/Compiler/test/inline.jl
@@ -1,5 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_inline
+
 using Test
 using Base.Meta
 using Core: ReturnNode
@@ -1857,7 +1859,7 @@ let i::Int, continue_::Bool
     ir = Compiler.ssa_inlining_pass!(ir, inlining, false)
     @test findfirst(isinvoke(:func_mul_int), ir.stmts.stmt) === nothing
     @test (i = findfirst(iscall((ir, Core.Intrinsics.mul_int)), ir.stmts.stmt)) !== nothing
-    lins = Base.IRShow.buildLineInfoNode(ir.debuginfo, nothing, i)
+    lins = Compiler.IRShow.buildLineInfoNode(ir.debuginfo, nothing, i)
     @test (continue_ = length(lins) == 2) # :multi_inlining1 -> :func_mul_int
     if continue_
         def1 = lins[1].method
@@ -1881,7 +1883,7 @@ let i::Int, continue_::Bool
     ir = Compiler.ssa_inlining_pass!(ir, inlining, false)
     @test findfirst(isinvoke(:func_mul_int), ir.stmts.stmt) === nothing
     @test (i = findfirst(iscall((ir, Core.Intrinsics.mul_int)), ir.stmts.stmt)) !== nothing
-    lins = Base.IRShow.buildLineInfoNode(ir.debuginfo, nothing, i)
+    lins = Compiler.IRShow.buildLineInfoNode(ir.debuginfo, nothing, i)
     @test_broken (continue_ = length(lins) == 3) # see TODO in `ir_inline_linetable!`
     if continue_
         def1 = lins[1].method
@@ -2309,3 +2311,5 @@ g_noinline_invoke(x) = f_noinline_invoke(x)
 let src = code_typed1(g_noinline_invoke, (Union{Symbol,Nothing},))
     @test !any(@nospecialize(x)->isa(x,GlobalRef), src.code)
 end
+
+end # module test_inline
diff --git a/Compiler/test/interpreter_exec.jl b/Compiler/test/interpreter_exec.jl
index 65f42a0c7b89b5..4972df1a272020 100644
--- a/Compiler/test/interpreter_exec.jl
+++ b/Compiler/test/interpreter_exec.jl
@@ -1,17 +1,11 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 # tests that interpreter matches codegen
+include("setup_Compiler.jl")
+
 using Test
 using Core.IR
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
-
 # test that interpreter correctly handles PhiNodes (#29262)
 let m = Meta.@lower 1 + 1
     @assert Meta.isexpr(m, :thunk)
diff --git a/Compiler/test/invalidation.jl b/Compiler/test/invalidation.jl
index c986cb298369ff..3f283fece4767a 100644
--- a/Compiler/test/invalidation.jl
+++ b/Compiler/test/invalidation.jl
@@ -1,5 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_invalidation
+
 # setup
 # -----
 
@@ -104,7 +106,7 @@ begin
     let rt = only(Base.return_types(pr48932_callee, (Any,)))
         @test rt === Any
         effects = Base.infer_effects(pr48932_callee, (Any,))
-        @test Compiler.Effects(effects) == Compiler.Effects()
+        @test effects == Compiler.Effects()
     end
 
     # run inference on both `pr48932_caller` and `pr48932_callee`
@@ -171,7 +173,7 @@ begin take!(GLOBAL_BUFFER)
     let rt = only(Base.return_types(pr48932_callee_inferable, (Any,)))
         @test rt === Int
         effects = Base.infer_effects(pr48932_callee_inferable, (Any,))
-        @test Compiler.Effects(effects) == Compiler.Effects()
+        @test effects == Compiler.Effects()
     end
 
     # run inference on both `pr48932_caller` and `pr48932_callee`:
@@ -233,7 +235,7 @@ begin take!(GLOBAL_BUFFER)
     let rt = only(Base.return_types(pr48932_callee_inlined, (Any,)))
         @test rt === Any
         effects = Base.infer_effects(pr48932_callee_inlined, (Any,))
-        @test Compiler.Effects(effects) == Compiler.Effects()
+        @test effects == Compiler.Effects()
     end
 
     # run inference on `pr48932_caller_inlined` and `pr48932_callee_inlined`
@@ -283,3 +285,5 @@ begin take!(GLOBAL_BUFFER)
     @test isnothing(pr48932_caller_inlined(42))
     @test "42" == String(take!(GLOBAL_BUFFER))
 end
+
+end # module test_invalidation
diff --git a/Compiler/test/irpasses.jl b/Compiler/test/irpasses.jl
index 412ff3b98cb193..0668cd7764bf7f 100644
--- a/Compiler/test/irpasses.jl
+++ b/Compiler/test/irpasses.jl
@@ -1,5 +1,7 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_irpasses
+
 using Test
 using Base.Meta
 using Core.IR
@@ -1996,3 +1998,5 @@ let code = Any[
     ir = Compiler.domsort_ssa!(ir, domtree)
     Compiler.verify_ir(ir)
 end
+
+end # module test_irpasses
diff --git a/Compiler/test/irutils.jl b/Compiler/test/irutils.jl
index d1a3a2ea57c359..c1616ad4a8fd0f 100644
--- a/Compiler/test/irutils.jl
+++ b/Compiler/test/irutils.jl
@@ -1,12 +1,6 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+include("setup_Compiler.jl")
 
 using Core.IR
 using .Compiler: IRCode, IncrementalCompact, singleton_type, VarState
@@ -68,7 +62,7 @@ macro fully_eliminated(ex0...)
 end
 
 let m = Meta.@lower 1 + 1
-    @assert Meta.isexpr(m, :thunk)
+    @assert isexpr(m, :thunk)
     orig_src = m.args[1]::CodeInfo
     global function make_codeinfo(code::Vector{Any};
                                   ssavaluetypes::Union{Nothing,Vector{Any}}=nothing,
diff --git a/Compiler/test/runtests.jl b/Compiler/test/runtests.jl
index ea3df3aa2855d0..6a38fce678ba0f 100644
--- a/Compiler/test/runtests.jl
+++ b/Compiler/test/runtests.jl
@@ -3,7 +3,10 @@ using Test, Compiler
 using InteractiveUtils: @activate
 @activate Compiler
 
-for file in readlines(joinpath(@__DIR__, "testgroups"))
-    file == "special_loading" && continue # Only applicable to Base.Compiler
-    include(file * ".jl")
+@testset "Compiler.jl" begin
+    for file in readlines(joinpath(@__DIR__, "testgroups"))
+        file == "special_loading" && continue # Only applicable to Base.Compiler
+        testfile = file * ".jl"
+        @eval @testset $testfile include($testfile)
+    end
 end
diff --git a/Compiler/test/setup_Compiler.jl b/Compiler/test/setup_Compiler.jl
new file mode 100644
index 00000000000000..a28a3f918aaf93
--- /dev/null
+++ b/Compiler/test/setup_Compiler.jl
@@ -0,0 +1,9 @@
+# This file is a part of Julia. License is MIT: https://julialang.org/license
+
+if !@isdefined(Compiler)
+    if Base.REFLECTION_COMPILER[] === nothing
+        using Base.Compiler: Compiler
+    else
+        const Compiler = Base.REFLECTION_COMPILER[]
+    end
+end
diff --git a/Compiler/test/ssair.jl b/Compiler/test/ssair.jl
index d6707e4dec9c24..17f25dd2c8a738 100644
--- a/Compiler/test/ssair.jl
+++ b/Compiler/test/ssair.jl
@@ -1,9 +1,11 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_ssair
+
 include("irutils.jl")
 
-using Base.Meta
-using Core.IR
+using Test
+
 using .Compiler: CFG, BasicBlock, NewSSAValue
 
 make_bb(preds, succs) = BasicBlock(Compiler.StmtRange(0, 0), preds, succs)
@@ -393,13 +395,7 @@ f_if_typecheck() = (if nothing; end; unsafe_load(Ptr{Int}(0)))
 
 let # https://github.com/JuliaLang/julia/issues/42258
     code = """
-        if !@isdefined(Compiler)
-            if Base.identify_package("Compiler") === nothing
-                import Base.Compiler: Compiler
-            else
-                import Compiler
-            end
-        end
+        using Base: Compiler
 
         function foo()
             a = @noinline rand(rand(0:10))
@@ -824,3 +820,5 @@ let cl = Int32[32, 1, 1, 1000, 240, 230]
     cl2 = ccall(:jl_uncompress_codelocs, Any, (Any, Int), str, 2)
     @test cl == cl2
 end
+
+end # module test_ssair
diff --git a/Compiler/test/tarjan.jl b/Compiler/test/tarjan.jl
index 49124bdf650fea..4fe46374a7f791 100644
--- a/Compiler/test/tarjan.jl
+++ b/Compiler/test/tarjan.jl
@@ -1,5 +1,9 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_tarjan
+
+using Test
+
 include("irutils.jl")
 
 using .Compiler: CFGReachability, DomTree, CFG, BasicBlock, StmtRange, dominates,
@@ -165,3 +169,5 @@ end
     test_reachability(100, 150; all_checks=false)
     test_reachability(100, 1000; all_checks=false)
 end
+
+end # module test_tarjan
diff --git a/Compiler/test/validation.jl b/Compiler/test/validation.jl
index 38dfa9705d542b..2d5dbe68e3e969 100644
--- a/Compiler/test/validation.jl
+++ b/Compiler/test/validation.jl
@@ -1,14 +1,10 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
+module test_validation
+
 using Test, Core.IR
 
-if !@isdefined(Compiler)
-    if Base.identify_package("Compiler") === nothing
-        import Base.Compiler: Compiler
-    else
-        import Compiler
-    end
-end
+include("setup_Compiler.jl")
 
 function f22938(a, b, x...)
     nothing
@@ -145,3 +141,5 @@ end
     @test count(e.kind === Compiler.SLOTNAMES_NARGS_MISMATCH for e in errors) == 1
     @test count(e.kind === Compiler.SIGNATURE_NARGS_MISMATCH for e in errors) == 1
 end
+
+end # module test_validation