diff --git a/crates/cli/tests/cli_run.rs b/crates/cli/tests/cli_run.rs
index 6bfb3cad4f..1c26d03f9d 100644
--- a/crates/cli/tests/cli_run.rs
+++ b/crates/cli/tests/cli_run.rs
@@ -1188,6 +1188,51 @@ mod cli_run {
                 out.assert_stdout_ends_with(expected_ending);
             }
         }
+
+        #[test]
+        #[cfg_attr(windows, ignore)]
+        fn run_packages_unoptimized() {
+            build_platform_host();
+
+            let expected_ending =
+                "Hello, World! This text came from a package! This text came from a CSV package!\n";
+            let runner = cli_utils::helpers::Run::new_roc()
+                .arg(CMD_RUN)
+                .arg(from_root("crates/cli/tests/fixtures/packages", "app.roc").as_path());
+
+            if ALLOW_VALGRIND {
+                let out = runner.run_with_valgrind();
+                out.assert_clean_success();
+                out.assert_stdout_ends_with(expected_ending);
+            } else {
+                let out = runner.run();
+                out.assert_clean_success();
+                out.assert_stdout_ends_with(expected_ending);
+            }
+        }
+
+        #[test]
+        #[cfg_attr(windows, ignore)]
+        fn run_packages_optimized() {
+            build_platform_host();
+
+            let expected_ending =
+                "Hello, World! This text came from a package! This text came from a CSV package!\n";
+            let runner = cli_utils::helpers::Run::new_roc()
+                .arg(CMD_RUN)
+                .arg(OPTIMIZE_FLAG)
+                .arg(from_root("crates/cli/tests/fixtures/packages", "app.roc").as_path());
+
+            if ALLOW_VALGRIND {
+                let out = runner.run_with_valgrind();
+                out.assert_clean_success();
+                out.assert_stdout_ends_with(expected_ending);
+            } else {
+                let out = runner.run();
+                out.assert_clean_success();
+                out.assert_stdout_ends_with(expected_ending);
+            }
+        }
     }
 
     // TODO not sure if this cfg should still be here: #[cfg(not(debug_assertions))]
@@ -1458,36 +1503,6 @@ mod cli_run {
         }
     }
 
-    #[test]
-    #[serial(multi_dep_thunk)]
-    #[cfg_attr(windows, ignore)]
-    fn run_packages_unoptimized() {
-        test_roc_app(
-            from_root("crates/cli/tests/fixtures/packages", "app.roc").as_path(),
-            vec![],
-            &[],
-            vec![],
-            "Hello, World! This text came from a package! This text came from a CSV package!\n",
-            UseValgrind::Yes,
-            TestCliCommands::Run,
-        );
-    }
-
-    #[test]
-    #[serial(multi_dep_thunk)]
-    #[cfg_attr(windows, ignore)]
-    fn run_packages_optimized() {
-        test_roc_app(
-            from_root("crates/cli/tests/fixtures/packages", "app.roc").as_path(),
-            vec![OPTIMIZE_FLAG],
-            &[],
-            vec![],
-            "Hello, World! This text came from a package! This text came from a CSV package!\n",
-            UseValgrind::Yes,
-            TestCliCommands::Run,
-        );
-    }
-
     #[test]
     #[serial(multi_dep_thunk)]
     #[cfg_attr(windows, ignore)]
diff --git a/crates/cli/tests/fixtures/multi-dep-str/Dep1.roc b/crates/cli/tests/fixtures/multi-dep-str/Dep1.roc
index c903b76dce..27d078d39e 100644
--- a/crates/cli/tests/fixtures/multi-dep-str/Dep1.roc
+++ b/crates/cli/tests/fixtures/multi-dep-str/Dep1.roc
@@ -1,4 +1,6 @@
-interface Dep1 exposes [str1] imports [Dep2]
+module [str1]
+
+import Dep2
 
 str1 : Str
 str1 = Dep2.str2
diff --git a/crates/cli/tests/fixtures/multi-dep-str/Dep2.roc b/crates/cli/tests/fixtures/multi-dep-str/Dep2.roc
index b4f446c079..cb2c1eca4d 100644
--- a/crates/cli/tests/fixtures/multi-dep-str/Dep2.roc
+++ b/crates/cli/tests/fixtures/multi-dep-str/Dep2.roc
@@ -1,4 +1,4 @@
-interface Dep2 exposes [str2] imports []
+module [str2]
 
 str2 : Str
 str2 = "I am Dep2.str2"
diff --git a/crates/cli/tests/fixtures/multi-dep-str/Main.roc b/crates/cli/tests/fixtures/multi-dep-str/Main.roc
index 68b60ec5e8..58e378ed1d 100644
--- a/crates/cli/tests/fixtures/multi-dep-str/Main.roc
+++ b/crates/cli/tests/fixtures/multi-dep-str/Main.roc
@@ -1,7 +1,6 @@
-app "multi-dep-str"
-    packages { pf: "../../test-platform-simple-zig/main.roc" }
-    imports [Dep1]
-    provides [main] to pf
+app [main] { pf: platform "../../test-platform-simple-zig/main.roc" }
+
+import Dep1
 
 main : Str
 main = Dep1.str1
diff --git a/crates/cli/tests/fixtures/multi-dep-thunk/Dep1.roc b/crates/cli/tests/fixtures/multi-dep-thunk/Dep1.roc
index b52416c426..a975704b4f 100644
--- a/crates/cli/tests/fixtures/multi-dep-thunk/Dep1.roc
+++ b/crates/cli/tests/fixtures/multi-dep-thunk/Dep1.roc
@@ -1,4 +1,6 @@
-interface Dep1 exposes [value1] imports [Dep2]
+module [value1]
+
+import Dep2
 
 value1 : {} -> Str
 value1 = \_ -> Dep2.value2 {}
diff --git a/crates/cli/tests/fixtures/multi-dep-thunk/Dep2.roc b/crates/cli/tests/fixtures/multi-dep-thunk/Dep2.roc
index 71b19dd775..c75c645283 100644
--- a/crates/cli/tests/fixtures/multi-dep-thunk/Dep2.roc
+++ b/crates/cli/tests/fixtures/multi-dep-thunk/Dep2.roc
@@ -1,4 +1,4 @@
-interface Dep2 exposes [value2] imports []
+module [value2]
 
 value2 : {} -> Str
 value2 = \_ -> "I am Dep2.value2"
diff --git a/crates/cli/tests/fixtures/multi-dep-thunk/Main.roc b/crates/cli/tests/fixtures/multi-dep-thunk/Main.roc
index 82f33c7dcf..00fb7fd151 100644
--- a/crates/cli/tests/fixtures/multi-dep-thunk/Main.roc
+++ b/crates/cli/tests/fixtures/multi-dep-thunk/Main.roc
@@ -1,7 +1,6 @@
-app "multi-dep-thunk"
-    packages { pf: "../../test-platform-simple-zig/main.roc" }
-    imports [Dep1]
-    provides [main] to pf
+app [main] { pf: platform "../../test-platform-simple-zig/main.roc" }
+
+import Dep1
 
 main : Str
 main = Dep1.value1 {}
diff --git a/crates/cli/tests/fixtures/multi-dep-thunk/platform/host.zig b/crates/cli/tests/fixtures/multi-dep-thunk/platform/host.zig
deleted file mode 100644
index 3859fd9015..0000000000
--- a/crates/cli/tests/fixtures/multi-dep-thunk/platform/host.zig
+++ /dev/null
@@ -1,119 +0,0 @@
-const std = @import("std");
-const builtin = @import("builtin");
-const str = @import("glue").str;
-const RocStr = str.RocStr;
-const testing = std.testing;
-const expectEqual = testing.expectEqual;
-const expect = testing.expect;
-
-const mem = std.mem;
-const Allocator = mem.Allocator;
-
-extern fn roc__mainForHost_1_exposed_generic(*RocStr) void;
-
-const Align = 2 * @alignOf(usize);
-extern fn malloc(size: usize) callconv(.C) ?*anyopaque;
-extern fn realloc(c_ptr: [*]align(@alignOf(u128)) u8, size: usize) callconv(.C) ?*anyopaque;
-extern fn free(c_ptr: [*]align(@alignOf(u128)) u8) callconv(.C) void;
-extern fn memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void;
-extern fn memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void;
-
-export fn roc_alloc(size: usize, alignment: u32) callconv(.C) ?*anyopaque {
-    _ = alignment;
-    return malloc(size);
-}
-
-export fn roc_realloc(c_ptr: *anyopaque, new_size: usize, old_size: usize, alignment: u32) callconv(.C) ?*anyopaque {
-    _ = old_size;
-    _ = alignment;
-    return realloc(@as([*]align(Align) u8, @alignCast(@ptrCast(c_ptr))), new_size);
-}
-
-export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
-    _ = alignment;
-    free(@as([*]align(Align) u8, @alignCast(@ptrCast(c_ptr))));
-}
-
-export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
-    return memset(dst, value, size);
-}
-
-export fn roc_panic(msg: *RocStr, tag_id: u32) callconv(.C) void {
-    const stderr = std.io.getStdErr().writer();
-    switch (tag_id) {
-        0 => {
-            stderr.print("Roc standard library crashed with message\n\n    {s}\n\nShutting down\n", .{msg.asSlice()}) catch unreachable;
-        },
-        1 => {
-            stderr.print("Application crashed with message\n\n    {s}\n\nShutting down\n", .{msg.asSlice()}) catch unreachable;
-        },
-        else => unreachable,
-    }
-    std.process.exit(1);
-}
-
-export fn roc_dbg(loc: *RocStr, msg: *RocStr, src: *RocStr) callconv(.C) void {
-    const stderr = std.io.getStdErr().writer();
-    stderr.print("[{s}] {s} = {s}\n", .{ loc.asSlice(), src.asSlice(), msg.asSlice() }) catch unreachable;
-}
-
-extern fn kill(pid: c_int, sig: c_int) c_int;
-extern fn shm_open(name: *const i8, oflag: c_int, mode: c_uint) c_int;
-extern fn mmap(addr: ?*anyopaque, length: c_uint, prot: c_int, flags: c_int, fd: c_int, offset: c_uint) *anyopaque;
-extern fn getppid() c_int;
-
-fn roc_getppid() callconv(.C) c_int {
-    return getppid();
-}
-
-fn roc_getppid_windows_stub() callconv(.C) c_int {
-    return 0;
-}
-
-fn roc_shm_open(name: *const i8, oflag: c_int, mode: c_uint) callconv(.C) c_int {
-    return shm_open(name, oflag, mode);
-}
-fn roc_mmap(addr: ?*anyopaque, length: c_uint, prot: c_int, flags: c_int, fd: c_int, offset: c_uint) callconv(.C) *anyopaque {
-    return mmap(addr, length, prot, flags, fd, offset);
-}
-
-comptime {
-    if (builtin.os.tag == .macos or builtin.os.tag == .linux) {
-        @export(roc_getppid, .{ .name = "roc_getppid", .linkage = .Strong });
-        @export(roc_mmap, .{ .name = "roc_mmap", .linkage = .Strong });
-        @export(roc_shm_open, .{ .name = "roc_shm_open", .linkage = .Strong });
-    }
-
-    if (builtin.os.tag == .windows) {
-        @export(roc_getppid_windows_stub, .{ .name = "roc_getppid", .linkage = .Strong });
-    }
-}
-
-const Unit = extern struct {};
-
-pub export fn main() i32 {
-    const stdout = std.io.getStdOut().writer();
-    const stderr = std.io.getStdErr().writer();
-
-    var timer = std.time.Timer.start() catch unreachable;
-
-    // actually call roc to populate the callresult
-    var callresult = RocStr.empty();
-    roc__mainForHost_1_exposed_generic(&callresult);
-
-    const nanos = timer.read();
-    const seconds = (@as(f64, @floatFromInt(nanos)) / 1_000_000_000.0);
-
-    // stdout the result
-    stdout.print("{s}\n", .{callresult.asSlice()}) catch unreachable;
-
-    callresult.decref();
-
-    stderr.print("runtime: {d:.3}ms\n", .{seconds * 1000}) catch unreachable;
-
-    return 0;
-}
-
-fn to_seconds(tms: std.os.timespec) f64 {
-    return @as(f64, @floatFromInt(tms.tv_sec)) + (@as(f64, @floatFromInt(tms.tv_nsec)) / 1_000_000_000.0);
-}
diff --git a/crates/cli/tests/fixtures/multi-dep-thunk/platform/main.roc b/crates/cli/tests/fixtures/multi-dep-thunk/platform/main.roc
deleted file mode 100644
index ad427260fa..0000000000
--- a/crates/cli/tests/fixtures/multi-dep-thunk/platform/main.roc
+++ /dev/null
@@ -1,9 +0,0 @@
-platform "multi-dep-thunk"
-    requires {}{ main : Str }
-    exposes []
-    packages {}
-    imports []
-    provides [mainForHost]
-
-mainForHost : Str
-mainForHost = main
diff --git a/crates/cli/tests/fixtures/packages/app.roc b/crates/cli/tests/fixtures/packages/app.roc
index 22918325c9..12487fb128 100644
--- a/crates/cli/tests/fixtures/packages/app.roc
+++ b/crates/cli/tests/fixtures/packages/app.roc
@@ -1,6 +1,10 @@
-app "packages-test"
-    packages { pf: "platform/main.roc", json: "json/main.roc", csv: "csv/main.roc" }
-    imports [json.JsonParser, csv.Csv]
-    provides [main] to pf
+app [main] {
+    pf: platform "../../test-platform-simple-zig/main.roc",
+    json: "json/main.roc",
+    csv: "csv/main.roc",
+}
+
+import json.JsonParser
+import csv.Csv
 
 main = "Hello, World! $(JsonParser.example) $(Csv.example)"
diff --git a/crates/cli/tests/fixtures/packages/csv/Csv.roc b/crates/cli/tests/fixtures/packages/csv/Csv.roc
index bc71f776d4..ce5afa7f4e 100644
--- a/crates/cli/tests/fixtures/packages/csv/Csv.roc
+++ b/crates/cli/tests/fixtures/packages/csv/Csv.roc
@@ -1,6 +1,4 @@
-interface Csv
-    exposes [example]
-    imports []
+module [example]
 
 example : Str
-example = "This text came from a CSV package!"
\ No newline at end of file
+example = "This text came from a CSV package!"
diff --git a/crates/cli/tests/fixtures/packages/json/JsonParser.roc b/crates/cli/tests/fixtures/packages/json/JsonParser.roc
index 2ebd6b1a62..1ff99b4540 100644
--- a/crates/cli/tests/fixtures/packages/json/JsonParser.roc
+++ b/crates/cli/tests/fixtures/packages/json/JsonParser.roc
@@ -1,6 +1,4 @@
-interface JsonParser
-    exposes [example]
-    imports []
+module [example]
 
 example : Str
-example = "This text came from a package!"
\ No newline at end of file
+example = "This text came from a package!"
diff --git a/crates/cli/tests/fixtures/packages/platform/host.zig b/crates/cli/tests/fixtures/packages/platform/host.zig
deleted file mode 100644
index 029a3ea4ed..0000000000
--- a/crates/cli/tests/fixtures/packages/platform/host.zig
+++ /dev/null
@@ -1,119 +0,0 @@
-const std = @import("std");
-const builtin = @import("builtin");
-const str = @import("glue").str;
-const RocStr = str.RocStr;
-const testing = std.testing;
-const expectEqual = testing.expectEqual;
-const expect = testing.expect;
-
-const mem = std.mem;
-const Allocator = mem.Allocator;
-
-extern fn roc__mainForHost_1_exposed_generic(*RocStr) void;
-
-const Align = 2 * @alignOf(usize);
-extern fn malloc(size: usize) callconv(.C) ?*align(Align) anyopaque;
-extern fn realloc(c_ptr: [*]align(Align) u8, size: usize) callconv(.C) ?*anyopaque;
-extern fn free(c_ptr: [*]align(Align) u8) callconv(.C) void;
-extern fn memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void;
-extern fn memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void;
-
-export fn roc_alloc(size: usize, alignment: u32) callconv(.C) ?*anyopaque {
-    _ = alignment;
-    return malloc(size);
-}
-
-export fn roc_realloc(c_ptr: *anyopaque, new_size: usize, old_size: usize, alignment: u32) callconv(.C) ?*anyopaque {
-    _ = old_size;
-    _ = alignment;
-    return realloc(@as([*]align(Align) u8, @alignCast(@ptrCast(c_ptr))), new_size);
-}
-
-export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
-    _ = alignment;
-    free(@as([*]align(Align) u8, @alignCast(@ptrCast(c_ptr))));
-}
-
-export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
-    return memset(dst, value, size);
-}
-
-export fn roc_panic(msg: *RocStr, tag_id: u32) callconv(.C) void {
-    const stderr = std.io.getStdErr().writer();
-    switch (tag_id) {
-        0 => {
-            stderr.print("Roc standard library crashed with message\n\n    {s}\n\nShutting down\n", .{msg.asSlice()}) catch unreachable;
-        },
-        1 => {
-            stderr.print("Application crashed with message\n\n    {s}\n\nShutting down\n", .{msg.asSlice()}) catch unreachable;
-        },
-        else => unreachable,
-    }
-    std.process.exit(1);
-}
-
-export fn roc_dbg(loc: *RocStr, msg: *RocStr, src: *RocStr) callconv(.C) void {
-    const stderr = std.io.getStdErr().writer();
-    stderr.print("[{s}] {s} = {s}\n", .{ loc.asSlice(), src.asSlice(), msg.asSlice() }) catch unreachable;
-}
-
-extern fn kill(pid: c_int, sig: c_int) c_int;
-extern fn shm_open(name: *const i8, oflag: c_int, mode: c_uint) c_int;
-extern fn mmap(addr: ?*anyopaque, length: c_uint, prot: c_int, flags: c_int, fd: c_int, offset: c_uint) *anyopaque;
-extern fn getppid() c_int;
-
-fn roc_getppid() callconv(.C) c_int {
-    return getppid();
-}
-
-fn roc_getppid_windows_stub() callconv(.C) c_int {
-    return 0;
-}
-
-fn roc_shm_open(name: *const i8, oflag: c_int, mode: c_uint) callconv(.C) c_int {
-    return shm_open(name, oflag, mode);
-}
-fn roc_mmap(addr: ?*anyopaque, length: c_uint, prot: c_int, flags: c_int, fd: c_int, offset: c_uint) callconv(.C) *anyopaque {
-    return mmap(addr, length, prot, flags, fd, offset);
-}
-
-comptime {
-    if (builtin.os.tag == .macos or builtin.os.tag == .linux) {
-        @export(roc_getppid, .{ .name = "roc_getppid", .linkage = .Strong });
-        @export(roc_mmap, .{ .name = "roc_mmap", .linkage = .Strong });
-        @export(roc_shm_open, .{ .name = "roc_shm_open", .linkage = .Strong });
-    }
-
-    if (builtin.os.tag == .windows) {
-        @export(roc_getppid_windows_stub, .{ .name = "roc_getppid", .linkage = .Strong });
-    }
-}
-
-const Unit = extern struct {};
-
-pub export fn main() i32 {
-    const stdout = std.io.getStdOut().writer();
-    const stderr = std.io.getStdErr().writer();
-
-    var timer = std.time.Timer.start() catch unreachable;
-
-    // actually call roc to populate the callresult
-    var callresult = RocStr.empty();
-    roc__mainForHost_1_exposed_generic(&callresult);
-
-    const nanos = timer.read();
-    const seconds = (@as(f64, @floatFromInt(nanos)) / 1_000_000_000.0);
-
-    // stdout the result
-    stdout.print("{s}\n", .{callresult.asSlice()}) catch unreachable;
-
-    callresult.decref();
-
-    stderr.print("runtime: {d:.3}ms\n", .{seconds * 1000}) catch unreachable;
-
-    return 0;
-}
-
-fn to_seconds(tms: std.os.timespec) f64 {
-    return @as(f64, @floatFromInt(tms.tv_sec)) + (@as(f64, @floatFromInt(tms.tv_nsec)) / 1_000_000_000.0);
-}
diff --git a/crates/cli/tests/fixtures/packages/platform/main.roc b/crates/cli/tests/fixtures/packages/platform/main.roc
deleted file mode 100644
index edc3368f93..0000000000
--- a/crates/cli/tests/fixtures/packages/platform/main.roc
+++ /dev/null
@@ -1,9 +0,0 @@
-platform "multi-module"
-    requires {}{ main : Str }
-    exposes []
-    packages {}
-    imports []
-    provides [mainForHost]
-
-mainForHost : Str
-mainForHost = main