diff --git a/src/lib/script.sh b/src/lib/script.sh
new file mode 100644
index 0000000..1894c36
--- /dev/null
+++ b/src/lib/script.sh
@@ -0,0 +1,101 @@
+#! /usr/bin/env bash
+
+# script.sh - utilitary functions.
+# Copyright (c) 2022 ge <https://nixhacks.net/>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+validate_sources() {
+    # Check sources array.
+    #
+    # Usage: validate_sources ARRAY
+
+    # Allowed URI schemes: file, mysql postgres, sqlite
+    # No required schemes.
+
+    local array=("$@")
+    local scheme=
+
+    for uri in "${array[@]}"; do
+        scheme="${uri%%:*}"
+        case "$scheme" in
+            file|mysql|postgres|sqlite) : ;; # do nothing, this is OK
+            *) echo "Error: Unsupported URI scheme: $scheme" >&2; exit 1;;
+        esac
+    done
+}
+
+validate_targets() {
+    # Check targets array.
+    #
+    # Usage: validate_targets ARRAY
+
+    # Allowed URI schemes: file, ftp, sftp, rsync, s3, swift, sj, dav, davs
+    # Required schemes (one or more times): file
+
+    local array=("$@")
+    local scheme=
+    local file_scheme=0
+
+    for uri in "${array[@]}"; do
+        scheme="${uri%%:*}"
+        case "$scheme" in
+            file|ftp|sftp|rsync|s3|swift|sj|dav|davs)
+                if [[ "$scheme" == file ]]; then
+                    (( file_scheme++ )) || true
+                fi
+            ;;
+            *) echo "Error: Unsupported URI scheme: $scheme" >&2; exit 1;;
+        esac
+    done
+
+    if [ "$file_scheme" -eq 0 ]; then
+        echo "Error: 'file' scheme is not set in targets." \
+            "You must provide one or more targets with 'file' scheme." >&2
+        exit 1
+    fi
+}
+
+source_script() {
+    # Safely as possible source backup script.
+    #
+    # Usage: source_script SCRIPT
+
+    local script="$1"
+
+    if ! test -f "$script"; then
+        echo "Error: No such file: $script" >&2; exit 1
+    fi
+
+    # Dry run script, check syntax. See set(1p)
+    if ! bash -n "$script"; then
+        echo Error: Please check your syntax >&2; exit 1
+    fi
+
+    # Source script
+    . "$@"
+
+    # Check required variables
+    if [[ "$sources" ]]; then
+        validate_sources "${sources[@]}"
+    else
+        echo Error: sources array is not set >&2; exit 1
+    fi
+
+    if [[ "$targets" ]]; then
+        validate_targets "${targets[@]}"
+    else
+        echo Error: targets array is not set >&2; exit 1
+    fi
+}
diff --git a/tests/files/bad_syntax.plan b/tests/files/bad_syntax.plan
new file mode 100644
index 0000000..9e765d8
--- /dev/null
+++ b/tests/files/bad_syntax.plan
@@ -0,0 +1,2 @@
+sources= ('file:/home/user')
+targets=('file:/var/backup')
diff --git a/tests/files/empty_script.plan b/tests/files/empty_script.plan
new file mode 100644
index 0000000..e69de29
diff --git a/tests/files/empty_sources.plan b/tests/files/empty_sources.plan
new file mode 100644
index 0000000..05533cd
--- /dev/null
+++ b/tests/files/empty_sources.plan
@@ -0,0 +1,2 @@
+sources=()
+targets=('file:/var/backup')
diff --git a/tests/files/empty_targets.plan b/tests/files/empty_targets.plan
new file mode 100644
index 0000000..3efc79e
--- /dev/null
+++ b/tests/files/empty_targets.plan
@@ -0,0 +1,2 @@
+sources=('file:/home/user')
+targets=()
diff --git a/tests/files/no_file_target.plan b/tests/files/no_file_target.plan
new file mode 100644
index 0000000..cdb9601
--- /dev/null
+++ b/tests/files/no_file_target.plan
@@ -0,0 +1,2 @@
+sources=(file:///)
+targets=(ftp://user:pass@host/path)
diff --git a/tests/files/unsupported_source_scheme.plan b/tests/files/unsupported_source_scheme.plan
new file mode 100644
index 0000000..7e5b940
--- /dev/null
+++ b/tests/files/unsupported_source_scheme.plan
@@ -0,0 +1,2 @@
+sources=('mongo:/user:password@localhost/database')
+targets=('file:/var/backup')
diff --git a/tests/files/unsupported_target_scheme.plan b/tests/files/unsupported_target_scheme.plan
new file mode 100644
index 0000000..04fffd3
--- /dev/null
+++ b/tests/files/unsupported_target_scheme.plan
@@ -0,0 +1,2 @@
+sources=('file:/home/user')
+targets=(scp://user:pass@host/path)
diff --git a/tests/source_script.bats b/tests/source_script.bats
new file mode 100644
index 0000000..2814add
--- /dev/null
+++ b/tests/source_script.bats
@@ -0,0 +1,58 @@
+#! /usr/bin/env bats
+
+# source_script() from lib/script.sh tests.
+# See: https://bats-core.readthedocs.io/en/latest/index.html
+
+setup() {
+    # Bats setup
+    load 'helpers/bats-support/load'
+    load 'helpers/bats-assert/load'
+    DIR="$( cd "$( dirname "$BATS_TEST_FILENAME" )" >/dev/null 2>&1 && pwd )"
+    PATH="$DIR/../src/lib:$PATH"
+}
+
+# ------------------------------ #
+# Do tests!                      #
+# ------------------------------ #
+
+@test "Bad script syntax" {
+    . script.sh
+    run source_script $DIR/files/bad_syntax.plan
+    assert_output --partial 'Error: Please check your syntax'
+}
+
+@test "Empty script" {
+    . script.sh
+    run source_script $DIR/files/empty_script.plan
+    assert_output --partial 'Error: sources array is not set'
+}
+
+@test "Empty sources array" {
+    . script.sh
+    run source_script $DIR/files/empty_sources.plan
+    assert_output --partial 'Error: sources array is not set'
+}
+
+@test "Empty targets array" {
+    . script.sh
+    run source_script $DIR/files/empty_targets.plan
+    assert_output --partial 'Error: targets array is not set'
+}
+
+@test "No targets with file URI scheme" {
+    . script.sh
+    run source_script $DIR/files/no_file_target.plan
+    assert_output --partial "Error: 'file' scheme is not set in targets. You must provide one or more targets with 'file' scheme."
+}
+
+@test "Unsuported source scheme" {
+    . script.sh
+    run source_script $DIR/files/unsupported_source_scheme.plan
+    assert_output --partial 'Error: Unsupported URI scheme: mongo'
+}
+
+@test "Unsuported target scheme" {
+    . script.sh
+    run source_script $DIR/files/unsupported_target_scheme.plan
+    assert_output --partial 'Error: Unsupported URI scheme: scp'
+}