diff --git a/.travis.yml b/.travis.yml
index f3d9e6b3..2a5a739d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,11 +7,12 @@ addons:
     - debian-sid
     packages:
     - shellcheck
-install: "pip install flake8"
+install: "pip install flake8 pytest-cov"
 script:
   - test/static_code_analysis.sh
   - yes "" | ./pmbootstrap.py init
   - ./pmbootstrap.py kconfig_check
+  - test/testcases_fast.sh
   - test/check_checksums.py
 notifications:
   - email: false
diff --git a/pmb/helpers/other.py b/pmb/helpers/other.py
index 9eee8bb8..be23e888 100644
--- a/pmb/helpers/other.py
+++ b/pmb/helpers/other.py
@@ -26,11 +26,14 @@ import pmb.helpers.run
 def folder_size(args, path):
     """
     Run `du` to calculate the size of a folder (this is less code and
-    faster than doing the same task in pure Python).
+    faster than doing the same task in pure Python). This result is only
+    approximatelly right, but good enough for pmbootstrap's use case:
+    <https://github.com/postmarketOS/pmbootstrap/pull/760>
 
     :returns: folder size in bytes
     """
     output = pmb.helpers.run.root(args, ["du", "--summarize",
+                                         "--apparent-size",
                                          "--block-size=1",
                                          path], return_stdout=True)
     ret = int(output.split("\t")[0])
diff --git a/test/static_code_analysis.sh b/test/static_code_analysis.sh
index cafc65ec..39e2e357 100755
--- a/test/static_code_analysis.sh
+++ b/test/static_code_analysis.sh
@@ -23,6 +23,7 @@ DIR="$(cd "$(dirname "$0")" && pwd -P)"
 cd "$DIR"/..
 sh_files="
 	./test/static_code_analysis.sh
+	./test/testcases_fast.sh
 	./aports/main/postmarketos-base/firmwareload.sh
 	./aports/main/postmarketos-mkinitfs/init.sh.in
 	./aports/main/postmarketos-mkinitfs/init_functions.sh
diff --git a/test/test_challenge_apk.py b/test/test_challenge_apk.py
index 27941c19..f1577aa8 100644
--- a/test/test_challenge_apk.py
+++ b/test/test_challenge_apk.py
@@ -60,7 +60,7 @@ def test_apk_challenge_contents_diff(args):
 
     # Second file
     apk_b = temp_path_outside + "/b.apk"
-    pmb.chroot.user(args, ["cp", "/etc/abuild.conf", temp_path + "/" + name])
+    pmb.chroot.user(args, ["cp", "/etc/motd", temp_path + "/" + name])
     pmb.chroot.user(args, ["tar", "-czf", "b.apk", name],
                     working_dir=temp_path)
 
diff --git a/test/test_folder_size.py b/test/test_folder_size.py
index 5a54143a..f2559906 100644
--- a/test/test_folder_size.py
+++ b/test/test_folder_size.py
@@ -39,13 +39,19 @@ def args(request):
 
 
 def test_get_folder_size(args, tmpdir):
-    # Write five 2 KB files to tmpdir
+    # Write five 200 KB files to tmpdir
     tmpdir = str(tmpdir)
     files = 5
     for i in range(files):
         pmb.helpers.run.user(args, ["dd", "if=/dev/zero", "of=" +
                                     tmpdir + "/" + str(i), "bs=1K",
-                                    "count=2", "conv=notrunc"])
+                                    "count=200", "conv=notrunc"])
 
-    # Check if the size is correct
-    assert pmb.helpers.other.folder_size(args, tmpdir) == 20480
+    # Check if the size is correct. Unfortunately, the `du` call
+    # in pmb.helpers.other.folder_size is not very accurate, so we
+    # allow 10kb of tolerance (good enough for our use case):
+    # <https://github.com/postmarketOS/pmbootstrap/pull/760>
+    tolerance = 10240
+    size = 204800 * files
+    result = pmb.helpers.other.folder_size(args, tmpdir)
+    assert (result < size + tolerance and result > size - tolerance)
diff --git a/test/test_repo.py b/test/test_repo.py
index b0ef6cdd..4dae0b7a 100644
--- a/test/test_repo.py
+++ b/test/test_repo.py
@@ -21,7 +21,6 @@ import sys
 import pytest
 import types
 import time
-import logging
 
 # Import from parent directory
 pmb_src = os.path.realpath(os.path.join(os.path.dirname(__file__) + "/.."))
@@ -108,22 +107,3 @@ def test_hash():
     url = "https://nl.alpinelinux.org/alpine/edge/testing"
     hash = "865a153c"
     assert pmb.helpers.repo.hash(url, 8) == hash
-
-
-def test_apkindex_files(args):
-    # Make sure, that we have a user's APKINDEX.tar.gz
-    pmb.build.package(args, "hello-world", args.arch_native)
-
-    # Reset the cache
-    del args.cache["apkindex_files"][args.arch_native]
-
-    # Fake the upstream folder to be the same as the normal packages folder
-    args.mirror_postmarketos = args.work + "/packages"
-
-    files = pmb.helpers.repo.apkindex_files(args)
-    for file in files:
-        assert os.path.exists(file)
-        logging.info(file)
-
-    # Test cache
-    assert files == pmb.helpers.repo.apkindex_files(args)
diff --git a/test/testcases_fast.sh b/test/testcases_fast.sh
new file mode 100755
index 00000000..7defb1da
--- /dev/null
+++ b/test/testcases_fast.sh
@@ -0,0 +1,27 @@
+#!/bin/sh -e
+
+# Disable slow testcases
+# aport_in_sync_with_git: clones Alpine's aports repo
+# aportgen: clones Alpine's aports repo
+# build: builds cross-compilers for aarch64 and armhf
+# version: clones Alpine's apk repo
+disabled="
+	aport_in_sync_with_git
+	aportgen
+	build
+	version
+"
+
+# Filter out disabled testcases
+enabled=""
+cd "$(dirname "$0")/.."
+for file in test/test_*.py; do
+	for test in $disabled; do
+		[ "test/test_${test}.py" = "$file" ] && continue 2
+	done
+	enabled="$enabled $file"
+done
+
+# Run enabled testcases with coverage enabled
+# shellcheck disable=SC2086
+pytest --cov=pmb $enabled